A new Tel Aviv University study, the first of its kind, has revealed that vultures, much like humans, experience changes in movement habits and social relationships as they age. Young vultures frequently move between roosting sites and “hang out with friends”. During adolescence, they spend about half their nights at a permanent roosting site (“home”) and the other half at other sites. In old age, however, vultures scale back on socializing, preferring to “stay home”. The study, which involved 142 Eurasian Griffon Vultures (Gyps fulvus) in Israel, is among the few to shed light on the behavioral changes in aging animals in the wild.

The study, led by Dr. Marta Acácio as part of her post-doctoral research in Dr. Orr Spiegel’s laboratory at Tel Aviv University’s School of Zoology, was conducted in collaboration with Prof. Noa Pinter-Wollman of the University of California, Los Angeles (UCLA) and several other researchers. The findings were published in the prestigious journal PNAS.

Dr. Marta Acácio.

Dr. Orr Spiegel. releasing tagged vultures (Photo credit: Tovale Solomon).

The Eagle Has Landed

Dr. Spiegel explains: “Vultures are a locally endangered species in Israel, with only about 200 individual vultures remaining. They are closely monitored to determine the best possible conservation methods. We thought about what else could be gleaned from the extensive database we have accumulated over the years and agreed it would be interesting to explore how vultures age. Tracking the same individuals in the wild over many years is often very challenging. However, the transmitters we use to monitor the population provided a rare opportunity to observe the aging process in vultures specifically and in animals generally”.

The researchers utilized a database accumulated over 15 years from GPS devices attached to 142 vultures that tracked them for periods of up to 12 years. The vulture, a social bird, sleeps in roosts on cliffs. By cross-referencing the vultures’ ages with the GPS data on their roosting sites, the researchers discovered that as the vultures aged, they increasingly preferred to stay at the same roosting site.

Aging vulture being monitored (Photo credit: Tovale Solomon).

Home Sweet Home

Dr. Spiegel: “It turns out that aging vultures behave a bit like humans and are more inclined to stay at home. When they’re young, vultures like to explore new sites and frequently move between places; the likelihood that a young vulture will sleep at the same site two nights in a row is low. When they reach adolescence at the age of five, this behavior stabilizes, and as adults they spend 50 percent of their nights at the same site and the other 50 percent at other sites. When they are old, from the age of 10 onwards, they no longer have the energy to be ‘out and about’, and return consistently to the same site. Furthermore, when adult vultures do change sites, they do so in a predictable pattern: for example, one night in Ein Avdat, the next in the Small Crater, and the next in Nahal Golhan, following a fixed order. Of course, it could be argued that older vultures move less not because they are old, but because they avoid taking risks in the first place, which is how they reached the age they did. But here we are talking about the exact same individual birds: those who were adventurous at the age of five became more sedentary by age ten”.

Elder Eagles’ Poisoning

According to Dr. Spiegel, these fascinating findings on the aging of birds also have very practical implications for conservation efforts. “This new study can help us better protect vultures’ roosting sites in the wild. Additionally, we have now seen that older vultures have fewer social connections, which can help us to prevent poisoning. The transmitters are connected to a system that sends an alert to the Israel Nature and Parks Authority, and to us by phone, if the vulture is not moving or has landed in a dangerous place, indicating that it may have been poisoned.

Collecting dead vultures following poisoning in the Golan Heights by Nature and Parks Authority rangers (Photo credit: Nature and Parks Authority).

Unfortunately, this happens frequently. The danger arises when a vulture descends on a poisoned goat carcass, not knowing that a farmer has poisoned the carcass in order to kill stray dogs. Being social birds, vultures do not come down alone, leading to the risk of dozens of vultures dying at once. Understanding how wide the poisoned vulture’s social circle is will significantly help in mitigating the damage”.

It is important to note that vultures play an important ecological role in the disposing of carcasses. Studies have shown that the extinction of vultures ultimately leads to the loss of human lives, due to the rise of diseases such as rabies. In India, for example, a recently published study revealed that the extinction of vultures due to poisoning resulted in the deaths of half a million people over the course of five years.

A new study at Tel Aviv University found that sponges in the Gulf of Eilat have developed an original way to keep predators away. The researchers found that the sponges contain an unprecedented concentration of the highly toxic mineral molybdenum (Mo). In addition, they identified the bacterium that enables sponges to store such high concentrations of this precious metal and unraveled the symbiosis between the two organisms. The study was led by PhD student Shani Shoham and Prof. Micha Ilan from TAU’s School of Zoology. The paper was published in the leading journal Science Advances.

Two Ph.D. candidate Shani Shoham (right) and Raz Marom (Moskovich) happy to finally collect a sponge sample (in the bag) after several dives.

The researchers explain that sponges are the earliest multicellular organisms known to science. They live in marine environments and play an important role in the earth’s carbon, nitrogen, and silicon cycles. A sponge can process and filter seawater 50,000 times its body weight daily. With such enormous quantities of water flowing through them, they can accumulate various trace elements – and scientists try to understand how they cope with toxic amounts of materials like arsenic and molybdenum. 

The Hidden Shine of the Sponge

PhD student Shani Shoham: “20 to 30 years ago, researchers from our lab collected samples of a rare sponge called Theonella conica from the coral reef of Zanzibar in the Indian Ocean and found a high concentration of molybdenum. Molybdenum is a trace element, important for metabolism in the cells of all animals including humans, and widely used in industry. In my research, I wanted to test whether such high concentrations are also found in this sponge species in the Gulf of Eilat, where it grows at depths of more than 27 meters. Finding the sponge and analyzing its composition I discovered that it contained more molybdenum than any other organism on earth: 46,793 micrograms per gram of dry weight.”

Here’s what it looks like under a light microscope: Molybdenum accumulation in the bacterium Entotheonella. You can see the blue in the vacuoles. (Photo: Shani Shoham).

Shoham adds: “Like all trace elements, molybdenum is toxic when its concentration is higher than its solubility in water. But we must remember that a sponge is essentially a hollow mass of cells with no organs or tissues. Specifically in Theonella conica, up to 40% of the body volume is a microbial society – bacteria, viruses, and fungi living in symbiosis with the sponge. One of the most dominant bacteria, called Entotheonella sp., serves as a ‘detoxifying organ’ for accumulating metals inside the body of its sponge hosts. Hoarding more and more molybdenum, the bacteria convert it from its toxic soluble state into a mineral”.

“We are not sure why they do this. Perhaps the molybdenum protects the sponge, by announcing: “I’m toxic! Don’t eat me!”, and in return for this service the sponge does not eat the bacteria and serves as their host”

Sponge Bling: The Search for Molybdenum

Molybdenum is in high demand, mostly for alloys (for example, high-strength steel). Still, according to Shoham, it would be impracticable to retrieve it from sponges. The concentration is very high, but when translated into weight we could only get a few grams from every sponge, and the sponge itself is relatively rare. Sponges are grown in marine agriculture, mostly for the pharmaceutical industry, but this is quite a challenging endeavor. Sponges are very delicate creatures that need specific conditions”.

Shoham continues: “On the other hand, future research should focus on the ability of Entotheonellasp. bacteria to accumulate toxic metals. A few years ago, our lab discovered huge concentrations of other toxic metals, arsenic (As) and barium (Ba), in a close relative of Theonella conica, called Theonella swinhoei, which is common in the Gulf of Eilat. In this case, too, Entotheonellawas found to be largely responsible for hoarding the metals and turning them into minerals, thereby neutralizing their toxicity. Continued research on the bacteria can prove useful for treating water sources polluted with arsenic, a serious hazard which directly affects the health of 200 million people worldwide”.

 Prof. Micha Ilan.