Featured Research

from universities, journals, and other organizations

Living on islands makes animals tamer

Date:
January 10, 2014
Source:
University of California - Riverside
Summary:
Biologists have found that island lizards are "tame" compared to their mainland relatives, confirming Charles Darwin's observations of island tameness. Darwin had noted that island animals often acted tame, and presumed that they had evolved to be so after coming to inhabit islands that lacked most predators. The researchers found island lizards were more accessible the farther the islands were from the mainland.

An adult leopard lizard photographed in Arizona. These lizards eat other lizards, insects, and even small mammals. They can accelerate, jump, and sprint quite rapidly during prey capture or escape from predators. Their name reflects their spotted skin, which is effective camouflage, but also their disposition and powerful jaws.
Credit: Theodore Garland, UC Riverside.

Most of us have seen pictures and probably YouTube videos of "tame" animals on the Galapagos Islands, the biological paradise that was Charles Darwin's major source of inspiration as he observed nature and gradually developed his ideas about the importance of natural selection as a mechanism by which populations of organisms would change -- evolve genetically -- across generations, eventually becoming better and better suited to life in their current conditions.

Related Articles


A corollary of Darwin's revolutionary idea was that organisms would also evolve to lose structures, functions, and behaviors they no longer needed when environmental circumstances changed. He noted that island animals often acted tame, and presumed that they had evolved to be so after coming to inhabit islands that lacked most predators.

But more than 150 years later that almost casual observation remained to come under scientific scrutiny. Today, a team of researchers from the University of California, Riverside, Indiana University Purdue University Fort Wayne and George Washington University published a study showing that island lizards are indeed "tame" as compared with their mainland relatives. The researchers were able to approach island lizards more closely than they could approach mainland lizards.

"Our study confirms Darwin's observations and numerous anecdotal reports of island tameness," said Theodore Garland, a professor of biology at UC Riverside and one of the paper's coauthors. "His insights have once again proven to be correct, and remain an important source of inspiration for present-day biologists."

Study results appear online in the Proceedings of the Royal Society B. They will appear in the journal in print on Feb. 22.

The researchers conducted analyses of relationships of flight initiation distance (the predator-prey distance when the prey starts to flee) to distance to mainland, island area, and occupation of an island for 66 lizard species, taking into account differences in prey size and predator approach speed. They analyzed island and mainland lizard species from five continents and islands in the Atlantic and Pacific Oceans and the Caribbean and Mediterranean Seas.

Their results showed that island tameness exists and that flight initiation distance decreases as distance from mainland increases. In other words, island lizards were more accessible the farther the islands were from the mainland.

"The suggestion by Darwin and others that prey on oceanic islands have diminished escape behavior is supported for lizards, which are distributed widely on both continents and islands," Garland said.

He explained that escape responses are reduced on remote islands, because predators are scarce or absent there, and natural selection under reduced predation favors prey that do not waste time and energy developing and performing needless escape.

The research team also found that prey size is an important factor that affects escape behavior.

"When prey are very small relative to predators, predators do not attack isolated individual prey," Garland said. "This results in the absence of fleeing or very short flight initiation distance."

The researchers found no conclusive evidence showing that flight initiation distance is related to island area. They found, however, that predator approach speed is an important factor in lizards.

"It is possible that other factors favor island tameness. For example, if food is scarce on islands, the cost of leaving food to flee would favor shortened flight initiation distance," Garland said.

Garland was joined in the study by William E. Cooper Jr. (first author of the research paper) at Indiana University Purdue University Fort Wayne, Ind., and R. Alexander Pyron at the George Washington University, Wash. D.C.

The study was supported in part by a grant from the National Science Foundation.


Story Source:

The above story is based on materials provided by University of California - Riverside. The original article was written by Iqbal Pittalwala. Note: Materials may be edited for content and length.


Journal Reference:

  1. W. E. Cooper, R. A. Pyron, T. Garland. Island tameness: living on islands reduces flight initiation distance. Proceedings of the Royal Society B: Biological Sciences, 2014; 281 (1777): 20133019 DOI: 10.1098/rspb.2013.3019

Cite This Page:

University of California - Riverside. "Living on islands makes animals tamer." ScienceDaily. ScienceDaily, 10 January 2014. <www.sciencedaily.com/releases/2014/01/140110103720.htm>.
University of California - Riverside. (2014, January 10). Living on islands makes animals tamer. ScienceDaily. Retrieved November 25, 2014 from www.sciencedaily.com/releases/2014/01/140110103720.htm
University of California - Riverside. "Living on islands makes animals tamer." ScienceDaily. www.sciencedaily.com/releases/2014/01/140110103720.htm (accessed November 25, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Tuesday, November 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

Newsy (Nov. 25, 2014) The US FDA is announcing new calorie rules on Tuesday that will require everywhere from theaters to vending machines to include calorie counts. Video provided by Newsy
Powered by NewsLook.com
Feast Your Eyes: Lamb Chop Sent Into Space from UK

Feast Your Eyes: Lamb Chop Sent Into Space from UK

Reuters - Light News Video Online (Nov. 25, 2014) Take a stab at this -- stunt video shows a lamb chop's journey from an east London restaurant over 30 kilometers into space. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Cambodian Capital's Only Working Elephant to Retire in Jungle

Cambodian Capital's Only Working Elephant to Retire in Jungle

AFP (Nov. 25, 2014) Phnom Penh's only working elephant was blessed by a crowd of chanting Buddhist monks Tuesday as she prepared for a life of comfortable jungle retirement after three decades of giving rides to tourists. Duration: 00:36 Video provided by AFP
Powered by NewsLook.com
Stray Dog Follows Adventure Racing Team for 6-Day Endurance Race

Stray Dog Follows Adventure Racing Team for 6-Day Endurance Race

Buzz60 (Nov. 24, 2014) A Swedish Adventure racing team travels to try and win a world title, but comes home with something way better: a stray dog that joined the team for much of the grueling 430-mile race. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins