Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Predators and Isolation Shape the Evolution of ‘Island Tameness,’ Providing Conservation Insights


Charles Darwin noted more than 150 years ago that animals on the Galapagos Islands, including finches and marine iguanas, were more docile than mainland creatures. He attributed this tameness to the fact that there are fewer predators on remote islands.

While “island tameness” is an old idea, there have been few rigorous studies of the phenomenon. Many aspects remain unclear, including the mechanisms behind it and the speed at which it evolves in island populations.

Photo by Johannes Foufopoulos

An Aegean wall lizard on the island of Naxos, Greece.

A new University of Michigan-led study of Aegean wall lizard populations on 37 Greek islands shows that island tameness is determined by both the diversity of the local predator populations and the length of time an island has been separated from the mainland.

The researchers found that as the diversity of predators on an island increases, so does the distance at which these small lizards start to flee when they are approached -- an anti-predator response which scientists call the flight initiation distance. In addition, they found that the longer an island has been isolated from the mainland, on average, the longer its resident Aegean wall lizards will wait before fleeing from a predator.

The results suggest that animals living on small, long-isolated islands face the greatest risk from introduced predators -- such as feral cats and rats -- and should therefore receive priority in conservation efforts, said U-M vertebrate ecologist Johannes Foufopoulos, co-author of a paper scheduled for online publication in the journal Evolution on Dec. 1.

“Being so fearless, these populations are extremely susceptible to any novel predator that’s introduced. In fact, island tameness has caused numerous island-species extinctions at the hands of human-introduced predators and pets,” said Foufopoulos, an associate professor at the U-M School of Natural Resources and Environment.

“Determining what factors lead to the loss of effective anti-predator responses is critical because it provides a fundamental understanding of evolutionary processes on islands and also helps conservation managers predict which island species are at most risk,” he said.

The first author of the Evolution paper is Kinsey M. Brock, who conducted the lizard study for her graduate thesis at the School of Natural Resources and Environment. “This is the first study to systematically test for the ecological factors that drive island tameness and the rate at which it can occur,” she said.

The study compared anti-predator responses of Aegean wall lizard populations on the Cyclades Islands in the central Aegean Sea to the composition of the predator communities and the isolation history of each island.

Site surveys were conducted to determine the resident lizard predators, which included rats; birds; vipers, sand boas and other snakes; feral cats; and stone martens.

Bathymetric data derived from navigation charts, targeted sonar measurements, and geomorphological reconstructions of past sea levels were used to determine how long each island has been separated from the Greek mainland. Some of the oldest islands have been cut off from the mainland for more than 450,000 years.

The researchers looked at how skittish the lizards were by measuring flight initiation distance, and they examined the likelihood that lizards will shed their tails by gently squeezing lizard tails between calipers in the laboratory. Tail-shedding, also know as tail autotomy, is a common but energetically costly anti-predator defense among lizards, who jettison the wriggling appendage when attacked and later grow a new tail.

Both the fear response and the propensity for tail-shedding were strongly associated with predator diversity on an island: The fewer predators present, the longer the lizards wait to flee and the weaker their tail-shedding ability.

“It would be evolutionary disadvantageous to shed your tail in a predator-free environment, as the fitness costs range from lowered social status to reduced locomotor ability and susceptibility to parasites,” Brock said.

The study showed that not all predators were equally important in shaping behavior. Fast-moving predators, such as mammals and hawks, were much more influential than sit-and-wait predators, such as vipers, in driving the evolution of shy, flighty lizards.

“This makes sense, as shyness is going to be a much less effective response against sit-and-wait predators that remain hidden until the prey is within striking distance,” Foufopoulos said.
The researchers also found that because larger islands tend to support more diverse predator populations, anti-predator responses were most dramatically lost on small, predator-poor islets. And lizards on the oldest islands tended to be the most fearless.

“In summary, our results indicate that loss of anti-predator defenses is a serious problem for island organisms and suggest that small, long-isolated island populations stand at the highest risk from invasive predators and, as such, should receive priority in conservation efforts,” Brock said.

The other authors of the Evolution paper are Peter Bednekoff of Eastern Michigan University and Panayiotis Pafilis of the University of Athens. The title of the paper is “Evolution of antipredator behavior in an island lizard species Podarcis erhardii (Reptilia: Lacertidae): the sum of all fears?”

The study received financial support from the School of Natural Resources and Environment, the U-M Museum of Zoology, the U-M International Institute and the SNRE Envoys.

Contact Information
Jim Erickson, (734) 647-1842,

Jim Erickson | newswise
Further information:

Further reports about: Environment Evolution Isolation Predators conservation diversity lizard populations tail

More articles from Ecology, The Environment and Conservation:

nachricht Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel

nachricht Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

For graphite pellets, just add elbow grease

23.03.2018 | Materials Sciences

Unique communication strategy discovered in stem cell pathway controlling plant growth

23.03.2018 | Agricultural and Forestry Science

Sharpening the X-ray view of the nanocosm

23.03.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>