Tag: Zoology

Outstanding Navigators, both Night and Day

Researchers find that bats navigate well, also during the day, thanks to their unique sensory integration.

It is time to bust a myth about bats – bats actually see well during the day and they know how to navigate the space during daylight hours. A new Tel Aviv University study has found that fruit bats use their biological sonar during the day, even though their vision is excellent and would ostensibly eliminate the need for the bats to emit calls to the environment and use their echoes to locate objects (echolocation). The researchers believe that due to the high accuracy of the bats’ bio-sonar system in estimating how far objects are, echolocation offers an additional tool – on top of vision – to help ensure that the bats are navigating as effectively as possible. This is similar to a person crossing the street using their sense of hearing as well as sight to make sure the road is clear.

Enjoying the Tel Aviv Sun

The study was conducted under the supervision of Prof. Yossi Yovel, head of Tel Aviv University’s Sagol School of Neuroscience and a researcher at the School of Zoology in The George S. Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History. The study was led by Ph.D. student Ofri Eitan in cooperation with Dr. Maya Weinberg, Dr. Sasha Danilovich, and Reut Assa, all from Tel Aviv University, and Yuval Barkai, an urban nature photographer. The study will be published in the journal Current Biology.

The researchers explain that in general, bats are active mainly at night, and echolocation is the tool they use to navigate their way in the dark. They also say, however, that in recent years a growing phenomenon has been witnessed in Israel, particularly in Tel Aviv but also in other cities, in which Egyptian fruit bats roam around even during the day. In the current study, the researchers sought to examine what happens when the bats are active during the day, and whether they are aided by their unique bio-sonar even in conditions of good visibility.

For the first time, the researchers studied the activity and sensory behavior of the fruit bat during the day. The research was conducted with the help of photography and audio recordings of the bats’ activities throughout the day, in three different situations: in the morning, as they went out to explore in Tel Aviv; later in the day, when they visited Tel Aviv’s sycamore trees; and while they were drinking water from an artificial pool. In each of these situations, the bats used echolocation.

Daytime Integration of Senses

Ofri Eitan explains: “We compared the bats’ landings and flights between the trees, and found that prior to landing, the bats increased the sounds they emitted in order to use the echoes to help estimate the distance to the ground. In addition, we found that even in the pools of water, bats increased the rate of their calls before coming into contact with the water and reduced it (and sometimes even ceased the calls completely) after ascending from the water to fly to an open area. On the other hand, there were cases in which the bats emerged from the pool and had a wall placed in front of them, and once again returned to the use of echolocation. So, all our results show that the fruit bats make functional use of echolocation.”

Prof. Yossi Yuval concludes: “Our results are unequivocal and show that fruit bats make frequent use of echolocation even during the day when visibility is good. We hypothesize that this is due to the fact that echolocation helps the bats to measure the distances of objects in the environment more accurately, and that their brains combine the visual information along with the auditory information. This study shows how important integration between different senses is, just as we humans integrate visual and auditory information when we cross a street, for example.”

Big Brains Helped Large Animals Survive Extinction

TAU researchers: more brain power helped animals adapt to changing conditions and increased chances of survival.

What do an elephant, a rhino and a hippopotamus all have in common? All three, along with other large animals, survived the mass extinction that took place for a period of about 120,000 years, starting from the time the last Ice Age began. In contrast, other huge animals, such as giant armadillos (weighing a ton), giant kangaroos and mammoths went extinct.

Researchers at Tel Aviv University and the University of Naples have examined the mass extinction of large animals over the past tens of thousands of years, and found that those species who survived extinction had, on average, much larger brains than those who did not. The researchers conclude that having a large brain (relative to body size) indicates relatively high intelligence and helped the surviving species adapt to changing conditions and cope with potential causes of extinction, such as human hunting.

The study was led by doctoral student Jacob Dembitzer of the University of Naples in Italy, Prof. Shai Meiri of Tel Aviv University’s School of Zoology and The Steinhardt Museum of Natural History, and Prof. Pasquale Raia and doctoral student Silvia Castiglione of the University of Naples. The study was published in the journal Scientific Reports.

Heavy Weight – No Guarantee

The researchers explain that the last Ice Age was characterized by the widespread extinction of large and giant animals on all continents on earth (except Antarctica). Among these:

  • America: Giant ground sloths weighing 4 tons, a giant armadillo weighing a ton, and mastodons
  • Australia: Marsupial diprotodon weighing a ton, giant kangaroos, and a marsupial ‘lion’
  • Eurasia: Giant deer, woolly rhinoceros, mammoth, and giant elephants weighing up to 11 tons

Other large animals, however, such as elephants, rhinos, and hippos, survived this extinction event and exist to this day.

The researchers also note that in some places, the extinction was particularly widespread:

  • Australia: The red and grey kangaroos are today the largest native animals
  • South America: The largest survivors are the guanaco and vicuña (similar to the llama, which is a domesticated animal) and the tapir, while many of the species weighing half a ton or more have become extinct

Brains over Body

Jacob Dembitzer: “We know that most of the extinctions were of large animals, and yet it is not clear what distinguishes the large extant species from those that went extinct. We hypothesized that behavioral flexibility, made possible by a large brain in relation to body size, gave the surviving species an evolutionary advantage – it has allowed them to adapt to the changes that have taken place over the last tens of thousands of years, including climate change and the appearance of humans. Previous studies have shown that many species, especially large species, went extinct due to over-hunting by humans that have entered their habitats. In this study, we tested our hypothesis for mammals over a period of about 120,000 years, from the time the last Ice Age began, and the time that modern man began to spread all over the world with lethal weapons, to 500 years before our time. This hypothesis even helps us explain the large number of extinctions in South America and Australia, since the large mammals living on these continents had relatively small brains.”

The researchers collected data from the paleontological literature on 50 extinct species of mammal from all continents, weighing from 11 kg (an extinct giant echidna) up to 11 tons (the straight-tusked elephant, which was also found in the Land of Israel), and compared the size of their cranial cavity to that of 291 evolutionarily close mammal species that survived and exist today, weighing from 1.4 kg (the platypus) up to 4 tons (the African elephant). They fed the data into statistical models that included the weighting of body size and phylogeny between different species.

Prof. Meiri: “We found that the surviving animals had brains 53% larger, on average than evolutionarily closely related, extinct species of a similar body size. We hypothesize that mammals with larger brains have been able to adapt their behavior and cope better with the changing conditions – mainly human hunting and possibly climate changes that occurred during that period – compared to mammals with relatively small brains.”

How are the Birds Coping with Climate Change?

Researchers detect changes in birds’ bodies, probably caused by global warming.

Researchers at Tel Aviv University have found changes in the morphology of many birds in Israel over the past 70 years, which they interpret to be a response to climate change. The body mass of some species decreased, while in others body length increased – in both cases increasing the ratio between surface area and volume. The researchers contend that these are strategies to facilitate heat loss to the environment: “The birds evidently changed in response to the changing climate. However, this solution may not be fully adequate, especially as temperatures continue to rise.”

Relying on the vast bird collection preserved by The Steinhardt Museum of Natural History at TAU, the researchers looked for changes in bird morphology over the past 70 years in Israel. They examined approximately 8,000 adult specimens of 106 different species – including migratory birds that annually pass through Israel (such as the common chiffchaff, white stork, and black buzzard), resident wild birds (like the Eurasian jay, Eurasian eagle-owl, and rock partridge), and commensal birds, that live near humans. They built a complex statistical model consisting of various parameters to assess morphological changes – in the birds’ body mass, body length and wing length – during the relevant period.

The study was led by Prof. Shai Meiri and PhD student Shahar Dubiner of the School of Zoology, The George S. Wise Faculty of Life Sciences, and the Steinhardt Museum of Natural History at Tel Aviv University. The paper was published in the scientific journal Global Ecology and Biogeography.

Cooling Down

Prof. Meiri explains that according to Bergmann’s rule, formulated in the 19th century, members of bird and mammal species living in a cold climate tend to be larger than members of the same species living in a warmer climate. This is because the ratio of surface area to volume is higher in smaller animals, permitting more heat loss (an advantage in warm regions), and lower in larger bodies, minimizing heat loss (a benefit in colder climates). Based on this rule, scientists have recently predicted that global warming will lead to a reduction in animal size, with a possible exception: birds living in the human environment (such as pigeons, house sparrows, and the hooded crow) may gain size due to increased food availability, a phenomenon already witnessed in mammals such as jackals and wolves.

Either Long or Slender

Shahar Dubiner: “Our findings revealed a complicated picture. We identified two different types of morphological changes: some species had become lighter – their mass had decreased while their body length remained unchanged; while others had become longer – their body length had increased, while their mass remained unchanged. These together represent more than half of the species examined, but there was practically no overlap between the two groups – almost none of the birds had become both lighter and longer. We think that these are two different strategies for coping with the same problem, namely the rising temperatures. In both cases, the surface area to volume ratio is increased (by either increasing the numerator or reducing the denominator) – which helps the body lose heat to its environment. The opposite, namely a decrease in this ratio, was not observed in any of the species.”

 

The researchers (from left to right): Shahar Dubiner and Prof. Shai Meiri

Global Phenomenon

Sadly, flying away from global warming is not an option. These findings were observed across the country, regardless of nutrition, and in all types of species: resident birds; commensal species living in the human environment – which, contrary to predictions, exhibited changes similar to those of other birds; and migrants.

A difference was identified, however, between the two strategies: changes in body length tended to occur more in migrants, while changes in body mass were more typical of non-migratory birds. The very fact that such changes were found in migratory birds coming from Asia, Europe, and Africa, suggests that we are witnessing a global phenomenon.

The study also found that the impact of climate change over time on bird morphology (the birds’ change in either weight or length over time, relative to the actual temperature change during that time) is ten times greater than the impact of similar differences in temperature between geographical areas (the birds’ differences in weight or length in different geographical areas, relative to the temperature differences between those areas).

What is the Limit of Evolutionary Flexibility?

Shahar Dubiner: “Our findings indicate that global warming causes fast and significant changes in bird morphology. But what are the implications of these changes? Should we be concerned? Is this a problem, or rather an encouraging ability to adapt to a changing environment? Such morphological changes over a few decades probably do not represent an evolutionary adaptation, but rather certain phenotypic flexibility exhibited by the birds. We are concerned that over such a short period of time, there is a limit to the flexibility or evolutionary potential of these traits, and the birds might run out of effective solutions as temperatures continue to rise.”

Featured image: Israeli birds have become either longer or slenderer over the past 70 years

Why do Locusts Form Destructive Swarms?

TAU researchers may have the answer.

Locust swarms that ruin all crops in their path have been a major cause of famine from Biblical times to the present. Over the last three years, large parts of Africa, India and Pakistan have been hard-hit by locust outbreaks, and climate change is expected to exacerbate the problem even further.

A new multidisciplinary study by experts in fields as varied as insect behavior and physiology, microbiology, and computational models of evolution, has led to valuable insights concerning locust swarming: “Locust swarms form when individual locusts, usually solitary and harmless, aggregate and begin to migrate. However, the causes for this behavior remain largely unknown, and an effective solution is yet to be found,” explains Prof. Amir Ayali from the School of Zoology at TAU’s George S. Wise Faculty of Life Sciences.

Following recent studies, indicating that microbiomes can influence their hosts’ social behavior, the researchers hypothesized that locusts’ microbiomes may play a role in changing the behavior of their hosts to become more ‘sociable’. The study was published in Environmental Microbiology.

The Bacteria that Fly with Borrowed Wings 

To test their hypothesis, the researchers examined the gut microbiomes of locusts reared in the laboratory, and found a profound change when individuals reared in solitary conditions joined a large group of about 200 locusts.

Omer Lavy: “The most significant change was observed in bacteria called Weissella, almost completely absent from the microbiome of solitary locusts, which became dominant soon after their hosts joined the group.”

The researchers then developed a mathematical model that was used for analyzing the conditions under which induction of locust aggregation produces significant evolutionary advantages for Weissella, allowing these bacteria to spread to numerous other hosts. Based on these results, the researchers hypothesize that Weissella bacteria may play an important role in the locust aggregation behavior. In other words, the bacteria may in some way encourage their hosts to change their behavior and become more ‘sociable’.

Prof. Ayali concludes:  “Our study contributes to the understanding of locust swarming – a leading cause of famine from antiquity to the present. Our findings do not prove unequivocally that the Weissella bacteria are responsible for the swarming and migration of locusts. The results do, however, suggest a high probability that the bacteria play an important role in inducing this behavior – a new hypothesis never previously proposed. We hope that this new understanding will drive the development of new means for combating locust outbreaks – still a major threat to countless people, animals, and plants all over the globe.”

The new study was based on a multidisciplinary collaboration of experts in fields as varied as insect behavior and physiology, microbiology, and computational models of evolution. The project was led by Prof. Amir Ayali and PhD student Omer Lavy from the School of Zoology at TAU’s George S. Wise Faculty of Life Sciences. Participants included Prof. Lilach Hadany, Ohad Lewin-Epstein and Yonatan Bendett from the School of Plant Sciences and Food Security and Prof. Uri Gophna from The Shmunis School of Biomedicine and Cancer Research, all of the Wise Faculty. They were joined by Dr. Eran Gefen from the University of Haifa-Oranim. 

How Can We Boost Our Fight Against Marine Plastic Pollution?

TAU researchers say global standardization must be established.

Plastic wastes endanger marine life in many ways: animals get entangled in large plastic items or swallow small particles and chemicals, consequently dying of suffocation, starvation or poisoning. Awareness is growing, and research is expanding, but the effort to monitor and prevent plastic pollution encounters many obstacles, first of all due to the enormous complexity and diversity of plastic debris.

A new review from Tel Aviv University has determined that global standardization of methodologies for monitoring and measuring marine plastic pollution can significantly boost international efforts to mitigate this troubling phenomenon. In a comprehensive survey of all methods described in existing literature, the researchers charted the great complexity and diversity of marine plastic pollution, which makes unified measurement and accurate evaluation very difficult. According to the researchers, this is precisely why a standardized system is urgently needed, enabling comparisons, exchange of information, and effective tools for decisionmakers.

Grave and Immediate Threat

The study was led by Gal Vered and Prof. Noa Shenkar of the School of Zoology at The George S. Wise Faculty of Life Sciences and The Steinhardt Museum of Natural History at Tel Aviv University. Gal Vered is also a researcher at the Interuniversity Institute for Marine Sciences in Eilat. The review was published in Current Opinion in Toxicology.

According to Prof. Shenkar, plastic pollution, which is all human-made, poses a grave and immediate threat to the marine environment, with constantly rising amounts of plastic entering the oceans. Thus, for example, a 2013 survey conducted by Israel’s Ministry of Environmental Protection found that plastic accounts for about 41% of the volume of waste produced annually by Israelis. The Covid-19 pandemic, which has generated extreme demands for personal protective and single-use products, has further exacerbated the problem.

Comes in Different Shapes and Forms

The researchers explain that marine plastic pollution comprises many different types of plastic and plastic products of various shapes and sizes – from huge ghost nets to nanoparticles, as well as a vast range of chemical additives. Different methods for monitoring, sampling, and identifying plastic pollution relate to different properties of the sampled material: from size, source, and original use, through shape and color, to chemical composition and physical properties. Sampling is usually conducted with a towed net, with the size of collected pollutants dependent on the net’s mesh size, and tiny particles are identified in the lab using various spectroscopic and chemical methods. In addition to the diversity in sampling and identification methods, units used for reporting measured concentrations of pollutants also vary: from the number of plastic objects per area, to the weight of particles per organism, and more.

“These differences generate confusion and lack of communication among researchers in different parts of the world, hampering our efforts to work together toward our common goal: providing decision makers with reliable data in order to promote the efforts to reduce plastic pollution and its many hazards,” explains Prof. Shenkar. “We are in urgent need of standardized methods and comparable measures for monitoring, sampling, identifying, classifying, and quantifying marine plastic pollution and its impact.”

International Collaboration Needed

“This study is a response to problems encountered in my research, which deals with the impact of plastic and its chemical additives on marine life in the Eilat coral reef (presenting Israel’s largest marine biodiversity),” says Gal Vered and explains: “The differences in methodology make it difficult to use the findings of other researchers – as either a source of information or for comparing results. Thus, for example, most measurements worldwide relate to samples obtained with a towed net from the surface of the water, while I wish to discover which materials reach the seafloor and reef organisms.”

“Standardization will enable accurate evaluations and valid comparisons between plastic pollutions in different places on the globe. This will maximize the power of scientific research, enhance our understanding of the impact of plastic pollution on ecosystems and marine life, and help us develop effective tools for decisionmakers facing this crucial issue.”

Prof. Shenkar concludes: “Marine plastic pollution is a global problem, which requires extensive international collaboration. At the bottom line, we all wish to focus our efforts and obtain the best results. Like many others, we believe that efforts should begin close to the shoreline, in areas directly impacted by plastic pollution. However, a great deal of research is still required in order to establish this assumption and build effective strategies for managing plastic pollution. But first of all, we urgently need standardization that will enable all of us, all over the world, to work together.”

Featured image: Prof. Noa Shenkar 

Over the Past 1.5 Million Years, Human Hunting Preferences have Wiped Out Large Animals

Breakthrough study tracks development of early humans’ hunting habits.

A groundbreaking study by researchers from Tel Aviv University tracks the development of humans’ hunting practices over the last 1.5 million years – as reflected in the animals we’ve hunted and consumed. The researchers believe that at any given time early humans preferred to hunt the largest animals available in their surroundings, which provided the greatest quantities of food in return for their effort.

In this way, according to the researchers, early humans repeatedly overhunted large animals to extinction and then went on to the next in size – while improving their hunting technologies to meet the new challenge. The researchers also claim that about 10,000 years ago, when animals larger than deer became extinct, humans began to domesticate plants and animals to supply their needs, which might explain why the agricultural revolution began in the Levant at precisely that time.

The study was conducted by Prof. Ran Barkai and Dr. Miki Ben-Dor of The Jacob M. Alkow Department of Archaeology and Ancient Near Eastern Cultures, Prof. Shai Meiri of the School of Zoology and The Steinhardt Museum of Natural History, and Jacob Dembitzer, a research student of Prof. Barkai and Prof. Meiri, who led the project. The paper was published in the prestigious scientific journal Quaternary Science Reviews.

The study, unprecedented in both scope and timespan, presents a comprehensive analysis of data on animal bones discovered at dozens of prehistoric sites in and around Israel. Findings indicate a continual decline in the size of game hunted by humans as their main food source – from giant elephants 1-1.5 million years ago down to gazelles 10,000 years ago. According to the researchers, these findings paint an illuminating picture of the interaction between humans and the animals around them over the last 1.5 million years.

Overhunting or Climate Changes?

Prof. Barkai notes two major issues presently addressed by prehistorians worldwide: What caused the mass extinction of large animals over the past hundreds of thousands of years – overhunting by humans or perhaps recurring climate changes? And what were the driving forces behind great changes in humankind – both physical and cultural – throughout its evolution?

Prof. Barkai: “In light of previous studies, our team proposed an original hypothesis that links the two questions: We think that large animals went extinct due to overhunting by humans, and that the change in diet and the need to hunt progressively smaller animals may have propelled the changes in humankind. In this study we tested our hypotheses in light of data from excavations in the Southern Levant covering several human species over a period of 1.5 million years.”

Prof. Ran Barkai

Jacob Dembitzer adds: “We considered the Southern Levant (Israel, the Palestinian Authority, Southwest Syria, Jordan, and Lebanon) to be an ‘archaeological laboratory’ due to the density and continuity of prehistoric findings covering such a long period of time over a relatively small area – a unique database unavailable anywhere else in the world. Excavations, which began 150 years ago, have produced evidence for the presence of humans, beginning with Homo erectus who arrived 1.5 million years ago, through the Neanderthals who lived here from an unknown time until they disappeared about 45,000 years ago, to modern humans (namely, ourselves) who came from Africa in several waves, starting around 180,000 years ago.”

The researchers collected all data available in the literature on animal bones found at prehistoric sites in the Southern Levant, mostly in Israel. These excavations, conducted from 1932 until today, provide a unique sequence of findings from different types of humans over a period of 1.5 million years. With some sites comprising several stratigraphic layers, sometimes thousands of years apart, the study covered a total of 133 layers from 58 prehistoric sites, in which thousands of bones belonging to 83 animal species had been identified. Based on these remains, the researchers calculated the weighted mean size of the animals in each layer at every site.

Prof. Meiri: “Our study tracked changes at a much higher resolution over a considerably longer period of time compared to previous research. The results were illuminating: we found a continual, and very significant, decline in the size of animals hunted by humans over 1.5 million years. For example, a third of the bones left behind by Homo erectus at sites dated to about a million years ago, belonged to elephants that weighed up to 13 tons (more than twice the weight of the modern African elephant) and provided humans with 90% of their food. The mean weight of all animals hunted by humans at that time was 3 tons, and elephant bones were found at nearly all sites up to 500,000 years ago.”

“Starting about 400,000 years ago, the humans who lived in our region – early ancestors of the Neandertals and Homo sapiens, appear to have hunted mainly deer, along with some larger animals weighing almost a ton, such as wild cattle and horses. Finally, in sites inhabited by modern humans, from about 50,000 to 10,000 years ago, approximately 70% of the bones belong to gazelles – an animal that weighs no more than 20-30kg. Other remains found at these later sites came mostly from fallow deer (about 20%), as well as smaller animals such as hares and turtles.”

Climate Change had Minimal Impact

Jacob Dembitzer: “Our next question was: What caused the disappearance of the large animals? A widely accepted theory attributes the extinction of large species to climate changes through the ages. To test this, we collected climatic and environmental data for the entire period, covering more than a dozen cycles of glacial and interglacial periods. This data included temperatures based on levels of the oxygen 18 isotope, and rainfall and vegetation evidenced by values of carbon 13 from the local Soreq Cave. A range of statistical analyses correlating between animal size and climate, precipitation, and environment, revealed that climate, and climate change, had little, if any, impact on animal extinction.”

According to Dr. Ben-Dor: “Our findings enable us to propose a fascinating hypothesis on the development of humankind: Humans always preferred to hunt the largest animals available in their environment, until these became very rare or extinct, forcing the prehistoric hunters to seek the next in size. As a result, to obtain the same amount of food, every human species appearing in the Southern Levant was compelled to hunt smaller animals than its predecessor, and consequently had to develop more advanced and effective technologies. Thus, for example, while spears were sufficient for Homo erectus to kill elephants at close range, modern humans developed the bow and arrow to kill fast-running gazelles from a distance.”

Environmental Damage from the Dawn of Humanity

Prof. Barkai concludes: “We believe that our model is relevant to human cultures everywhere. Moreover, for the first time, we argue that the driving force behind the constant improvement in human technology is the continual decline in the size of game. Ultimately, it may well be that 10,000 years ago in the Southern Levant, animals became too small or too rare to provide humans with sufficient food, and this could be related to the advent of agriculture. In addition, we confirmed the hypothesis that the extinction of large animals was caused by humans – who time and time again destroyed their own livelihood through overhunting. We may therefore conclude that humans have always ravaged their environment but were usually clever enough to find solutions for the problems they had created – from the bow and arrow to the agricultural revolution. The environment, however, always paid a devastating price.”

Featured image: Prof. Shai Meiri of the School of Zoology and The Steinhardt Museum of Natural History

How Do Bats Get Street-Smart?

TAU researchers find that baby fruit bats acquire their boldness from their adoptive mothers.

Tel Aviv University researchers conducted the first ever “cross-adoption” behavioral study in bats, whereby pups of urban fruit bats were adopted by rural mothers and vice versa in order to learn whether the relative boldness of city bats is a genetic or acquired trait. Prof. Yovel: “We wanted to find out whether boldness is transferred genetically or learned somehow from the mother. Our findings suggest that this trait is passed on to pups by the mothers that nurse and raise them, even when they are not their biological mothers.” Thus, the bat species’ willingness to take risks is an acquired rather than hereditary trait, passed on in some way from mother to young pup

The study was led by TAU’s Prof. Yossi Yovel, Head of the Sagol School of Neuroscience, member of the School of Zoology at The George S. Wise Faculty of Life Sciences and The Steinhardt Museum of Natural History, and recipient this year of the Blavatnik Young Scientists Award in Israel and the Kadar Family Award for Outstanding Research at TAU. It was conducted by Dr. Lee Harten, Nesim Gonceer, Michal Handel and Orit Dash from Prof. Yovel’s laboratory, in collaboration with Prof. H. Bobby Fokidis from Rollins College in Florida. The paper was published in BMC Biology.

Rural Bats More Risk Adverse

Dr. Harten explains: “While most animals do not live in an urban environment, some species thrive in it. We are trying to understand how they do this. Fruit bats are an excellent example of a species that has adapted well to the human environment of the city. Bat colonies thrive in Tel Aviv and other cities, while other colonies still live in rural areas. Research has shown that city-adapted fruit-bats tend to be bolder and take more risks than those living in the wild. We wanted to examine, under laboratory conditions, whether this trait is genetic or acquired.

In a preliminary experiment the researchers placed food inside a box that required adult bats to land and enter in order to get the food. They found that urban bats solved the problem immediately, while rural bats hesitated and took several hours to learn the trick. Prof. Yovel: “Similar results were observed in past experiments with birds: birds living in the city take more risks than birds of the same species residing in rural areas. Our study was the first to test this issue in bats.”

Bat Boldness: Genetic or Acquired?

The next step was testing whether this boldness is a hereditary trait, or a quality acquired by experience. To this end, the researchers conducted the same experiment with young bat pups, still fed by their mothers, who had never searched for food independently. They found that the urban pups, just like their parents, are bolder and learn faster than their rural counterparts.

Prof. Yovel: “These findings first led us to think that boldness is hereditary – passed on genetically from the urban parents to their pups. However, we know that young pups are still exposed to their mothers after birth. We decided to check whether pups learn from their mothers or are influenced by them in some other way.”

To answer this question, the researchers introduced a cross-adoption method: pups born to urban mothers were raised by rural mothers, and vice versa. They note that this was the first experiment of this type ever conducted in bats, and also the first ‘nature vs. nurture’ study for boldness in urban animals.

Liquid Courage?

Dr. Harten: “We found that the pups behaved like their adoptive mothers, not like their biological mothers. This means that boldness is an acquired rather than hereditary trait, passed on in some way from mother to young pup. We hypothesize that the agent may be some substance in the mother’s milk.” In an additional experiment the researchers discovered that the urban mothers’ milk contains a higher level of the hormone cortisol than the milk of rural mothers. It has not yet been ascertained, however, that this is the agent for the inter-generational transfer of boldness.

Prof. Yovel concludes: “The urban environment presents animals with more challenges and a greater variety of situations. It is therefore plausible that bats and other animals living in the city require more boldness and higher learning skills. In our study we focused on bat pups, examining whether bold behavior is the result of genetics, environment, or some combination between the two. In light of our findings, we hypothesize that the trait is passed on to pups in early stages of development, through some component of their mothers’ milk.” Dr. Harten adds: “We believe that a better understanding of the needs and behaviors of urban animals can help us protect them and adapt urban development to their needs.” 

Featured image: “Baby bat with its adoptive mother (Photo: Yuval Barkai)”

Revisiting the Tel Aviv Zoo

Two TAU students developed an app that recreates the mythological zoo in the heart of the city.

For many years, there was a zoo right in the center of Tel Aviv. Residents of nearby streets used to wake up to roars of tigers and monkeys’ chatter. In 1980, the zoo and its residents were relocated to a large complex in neighboring Ramat Gan, but seasoned Tel Avivians still think of it fondly. Maya Shekel and Yuval Kela, two talented students in the digital media track at The Steve Tisch School of Film and Television, wanted to see it with their own eyes, and developed the TAZOO app that enables this.

Throughout the four years of their studies, they designed and created the unique widget, based on stories and memories of the local community. The animals were created by help of augmented reality technology, and in order to experience the project in full, all you need to do is to download the app on your phone, make your way to Tel Aviv’s City Garden and look for the orange signs that are scattered in the garden.

This new attraction, which will soon be launched in a festive ceremony, has already warmed the hearts of several Tel Aviv residents who inspired the creation of the project and the stories, as well as Tel Aviv Mayor, Mr. Ron Huldai, who still recalls the exact wording on the garden signs.

The Next-door Neighbor

What brings two students, both born long after the zoo was closed, to recreate Tel Aviv’s animalistic past? “I’ve been living on Tel Aviv’s Hadassah Street all my life, right opposite where the zoo used to be,” says Maya Shekel. “Whenever people hear where I live, they ask me, ‘Did you know that there used to be a zoo there?’,” Therefore, after hearing the recurring questions for years, she decided to investigate the subject further together with Yuval Kela, who is also her life partner.

“After some online research, we discovered amazing photos of elephants and lions in the middle of Tel Aviv. We realized that the place used to be a cultural center for the residents of the city. We decided to start a Facebook group which we called ‘Tel Aviv Zoo Community’. Gradually, people would join the group and share photos, memories and stories about the zoo. This way, we got confirmation that there was a nostalgic need to revive the lost zoo, and to share its story with those who visit the place today, unaware of its history.”

 

“An elephant is about to join us,” Maya Shekel demonstrates to Tel Aviv Mayor Ron Huldai how the TAZOO app works

Reviving Animals in Augmented Reality

Unlike many apps that allow you to sit in your living room and feel like you’re somewhere else, Maya and Yuval chose to encourage their users to venture to the real site where the zoo was once located. “It was important for us to create an experience where people actually had to physically experience the sights and the feelings, while reviving the lost place,” explains Yuval.

Their main challenge was to adapt the app for two different target audiences: the older residents, who wish to reminisce, and to the younger target audience (such as the elderly residents’ children and grandchildren). “We overcame this hurdle by adding layers to the app, like short films about the zoo staff and additional information where you can choose to delve deeper and read more about each station. We also added some games that are more suitable for children,” he adds.  

For big and for small. The virtual zoo in the Hadassah Garden

Storytelling and Technology

During their studies, Maya and Yuval learned the importance of storytelling on platforms of this type. They made sure to study the technology thoroughly to get a good grasp of both its advantages and limitations.

Throughout their work on the app, more and more ideas for future projects were born. “We’re constantly thinking of how we can take the idea and expand on it to include more destinations in the city, in Israel and in the world. There’s no shortage on ‘lost’ places that have left memories and history that can be revived by help of technology, allowing for people to experience and learn about them,” says Maya.

“The technology is constantly evolving. We hope to continue to create significant impact by combining storytelling and innovative technology. Our dream is to constantly create mainly projects that are accessible to the general public,” she concludes. On the question of which animal she would not want us to miss on the TAZOO app, she says “We would not want you to miss out on our hippos, Paula and Jacob! They jump into the water and really blend in with the physical space.”

 

Paula and Jacob with friends

The project was supported by the Tel Aviv-Yafo Municipality, which cooperated and placed the signs throughout the park, as well as The New Fund for Cinema and TV, which supported and assisted with funding.

Download the app on iOS- https://apps.apple.com/ch/app/tazoo/id1548925102

Download the app on Android- https://play.google.com/store/apps/details?id=com.tazoo.tazoo

*Maya and Yuval hope to create an English version of the app in the very near future, as part of the existing one.

Like Teenagers on Vacation

Light pollution can impair crickets’ reproductive process and threaten their survival.

A joint study conducted by researchers from Tel Aviv University and the Open University of Israel revealed that exposing male crickets to artificial light at night (ALAN) can impair their activity cycles. According to the researchers, nocturnal chirping is the male’s way of calling females to come and mate with him, and its disruption can interfere with reproduction processes and even endanger the entire species. Previous studies worldwide have shown that light pollution is harmful to many species of animals and plants. The researchers call for reducing ALAN as much as possible to enable coexistence in the night environment.

Humans are Driving Away the Darkness

Keren Levy of the School of Zoology and the Steinhardt Museum of Natural History at Tel Aviv University explains: “The distinction between day and night, light and darkness, is a major foundation of life on earth. But humans, as creatures of the day who fear the dark, disrupt this natural order: they produce artificial light that drives away the darkness and allows them to continue their activities at night.”

Levy explains that today, more than 80% of the world population live under light pollution, and the overall extent of artificial light at night rises by 5% every year. This negatively impacts the environment and affects natural behaviors that have developed over millions of years of evolution. The artificial light at night affects the length and quality of sleep of many animals, leads to high mortality, and changes the activity cycles of many creatures. For example, dung beetles, that navigate using the Milky Way, lose their way when light pollution increases; sea turtles hatchlings seek the brightest surface in sight – supposedly the sea, and reach the nearby promenade instead; to mention just two of many examples.

Off-Tune Crickets

In the current study the researchers examined the impact of light pollution on the field cricket, a nocturnal insect whose chirping can be heard during the nights of late summer – when males call for females to mate with them.

Prof. Amir Ayali, also from TAU’s School of Zoology and the Steinhardt Museum of Natural History, explains, “In nature, crickets exhibit a very regular cycle of activity. Chirping behavior, calling for females, occurs at sunset and during the night, ending in the morning. We exposed field crickets to different levels of lifelong ALAN and observed its impact on two fundamental behaviors: chirping and locomotion.”

The researchers monitored dozens of crickets that were exposed throughout their lives (from egg to adult stage) to four types of light conditions. They found that crickets whose light-dark cycle is disrupted behave like teenagers on vacation: active or asleep according to their own inner clock or lacking any rhythm whatsoever.

“In fact,” adds Keren Levy, “light pollution induced by humankind impacts the field cricket and evokes loss of synchronization within the individual, on the population level, and between the population and the environment. Our findings on ALAN-induced changes in calling song patterns may possibly impair female attraction and reproduction in this species. Our results are in accord with many other studies demonstrating the severe impacts of low levels of ALAN on nature.”

Levy urges us all to help protect our environment and surroundings by turning off the lights in our backyards, on the terrace, in parking lots, and wherever possible: “Help us bring the night and the milky way back into our lives and enable nightly coexistence with the creatures around us.”

The study was led by Prof. Amir Ayali and Keren Levy of the School of Zoology and the Steinhardt Museum of Natural History at Tel Aviv University and Prof. Anat Barnea of the Department of Natural and Life Sciences at the Open University. Yoav Wegrzyn from Prof. Ayali’s laboratory and Ronny Efronny also took part in the study. The paper was published in Proceedings of the Royal Society B, and also mentioned in Nature.

Featured image: Prof. Amir Ayali and a small friend (Photo: Jonathan Blum)

Seahorses – Slow, but Fierce

Terrible swimmers with incredible preying capability.

Seahorses are not exactly Olympic swimmers, in fact they’re considered to be particularly poor swimmers. Despite being relatively slow, however, they are adept at preying on small, quick-moving animals. In a new study conducted at Tel Aviv University, researchers have succeeded in characterizing the incredible preying capability of seahorses, discovering that they can move their head up at the incredible speed of 0.002 seconds. The rapid head movement is accompanied by a powerful flow of water that snags their prey right into the seahorse’s mouth. How was this spring mechanism formed? When did it develop? The researchers hope the recent study will lead to further studies designed to help solve the riddle of spring fish.

The study was led by Prof. Roi Holzman and the doctoral student Corrine Jacobs of the School of Zoology at The George S. Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History at Tel Aviv University, and was conducted at the Interuniversity Institute for Marine Sciences in Eilat. The study was published in the Journal of Experimental Biology.

Springing to Action

The researchers explain that seahorses are fish that possess unique properties such as male ‘pregnancy’, square tail vertebrae, and of course the unique eating system. For most of the day, seahorses are anchored with their tail to seaweeds or corals with their head tilted downward, close to their body. However, when they detect prey passing over them, they lift their head at incredible speed and catch it. According to Prof. Holzman, while preying, seahorses turn their body into a kind of spring: using their back muscles, they stretch an elastic tendon, and use their neck bones as a ‘trigger’, just like a crossbow. The result is faster than even the fastest muscle contraction found anywhere in the animal world.

However, until now it was not clear how the spring-loaded mechanism enabled seahorses to actually eat. Just as anyone who tries to remove a fly from a cup of tea knows, water is a viscous medium and the fish needs to open its mouth to create a flow that draws the prey in. But how do seahorses coordinate snagging in prey with their head movement?

In their recent study, researchers from Tel Aviv University succeeded in characterizing and quantifying seahorse movement by photographing their attack at a speed of 4,000 images per second, and using a laser system for imaging water flows. This measurement showed that the ‘crossbow’ system serves two purposes: facilitating head movement and generating high velocity suction currents – 10 times faster than those of similar-sized fish. These advantages enable seahorses to catch particularly elusive prey.

Evolution of the Spring Mechanism

The new measurements also help shed light on the ecology of various species of seahorses, distinguished from each other by the length of their noses. “Our study shows that the speed of head movement and suction currents are determined by the length of a seahorse’s nose”, Prof. Holzman added. “From the evolutionary aspect, seahorses must choose between a short nose for strong suction and moderate head raising, or a long nose for rapid head raising and weaker suction currents. This choice, of course, corresponds to the available diet: long-nosed species catch smaller, quicker animals whereas short-nosed species catch heavier, more ponderous ones.”

 

Prof. Roi Holzman hopes the recent study will lead to further studies to help solve the riddle of spring fish

According to Prof. Holzman, seahorses are not the only instance of the impressive spring mechanism. Actually, seahorses are counted among the family of fish bearing the appropriate scientific name Misfit Fish, including species such as alligator pipefish, shrimpfish, and cornetfish or flutemouths.

“These fish are called that because of their odd shape which enables stretching their body into a spring. The big question applies to the evolution of the spring mechanism, how it was formed and when it developed. I hope our recent study will lead to further studies designed to help solve the riddle of spring fish”. 

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