Featured Research

from universities, journals, and other organizations

High Hormone Levels In Seabird Chicks Prepare Them To Kill Their Siblings

Date:
June 23, 2008
Source:
Wake Forest University
Summary:
The Nazca booby, a Galápagos Island seabird, emerges from its shell ready to kill its brother or sister. Biologists have linked the murderous behavior to high levels of testosterone and other male hormones found in the hatchlings.

Nazca booby chick.
Credit: Image courtesy of Wake Forest University

The Nazca booby, a Galápagos Island seabird, emerges from its shell ready to kill its brother or sister. Wake Forest University biologists and their colleagues have linked the murderous behavior to high levels of testosterone and other male hormones found in the hatchlings.

The elevated levels of male hormones, called androgens, increase aggression in both male and female chicks and prepare the birds to fight to the death as soon as they hatch, said David J. Anderson, professor of biology at Wake Forest and project leader.

Much of the field work was completed by Martina Müller, while she was a graduate student at Wake Forest.

"The older of two Nazca booby hatchlings unconditionally attacks and ejects the younger from the nest within days of hatching," Anderson said. Because Nazca boobies have difficulty raising more than one chick, it is important for the older chick to vanquish the younger one in order to increase its own chances of survival.

According to the study, the high hormone levels also cause the surviving chicks to behave like bullies after they grow up. They frequently seek out nestlings in their colony, and during those visits they often bite and push around the defenseless youngsters.

Blood samples were taken from Nazca booby chicks within 24 hours of hatching. In 15 nests with two eggs, blood samples were taken from both hatchlings. Samples were also taken from 15 hatchlings in one-egg nests. Then, blood hormones were analyzed by researchers at the University of Maryland, who co-authored the study. For comparison, the researchers did the same for blue-footed boobies, a closely related species.

The researchers suspect that the Nazca booby hatchlings experience the high level of aggression-related hormone during a "sensitive period" in their growth, when long-term growth patterns are easily affected.

Some Nazca booby nestlings experience a one-two hormonal punch, raising their aggression hormones even higher when they actually have a nest mate. The nestlings that fight siblings become bigger bullies as adults than the Nazca booby nestlings who never fight.

"The hormones that are part of this epic battle early in life seem to permanently change some aspects of their social personality," Anderson said.

Nazca booby chicks have aggression-related hormone levels three times as high as their less aggressive cousins, the blue-footed boobies. Blue-footed boobies do not have the same lethal fights right after hatching and do not go on to bully their fellow birds as adults.

The research is part of a long-term study by Anderson that has included monitoring more than 16,000 Nazca booby nests at Punta Cevallos, Isla Espanola, in the Galápagos Islands since 1984.


Story Source:

The above story is based on materials provided by Wake Forest University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Müller et al. Perinatal Androgens and Adult Behavior Vary with Nestling Social System in Siblicidal Boobies. PLoS One, 2008; 3 (6): e2460 DOI: 10.1371/journal.pone.0002460

Cite This Page:

Wake Forest University. "High Hormone Levels In Seabird Chicks Prepare Them To Kill Their Siblings." ScienceDaily. ScienceDaily, 23 June 2008. <www.sciencedaily.com/releases/2008/06/080618172949.htm>.
Wake Forest University. (2008, June 23). High Hormone Levels In Seabird Chicks Prepare Them To Kill Their Siblings. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2008/06/080618172949.htm
Wake Forest University. "High Hormone Levels In Seabird Chicks Prepare Them To Kill Their Siblings." ScienceDaily. www.sciencedaily.com/releases/2008/06/080618172949.htm (accessed September 18, 2014).

Share This



More Plants & Animals News

Thursday, September 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Chimp Violence Study Renews Debate On Why They Kill

Chimp Violence Study Renews Debate On Why They Kill

Newsy (Sep. 17, 2014) — The study weighs in on a debate over whether chimps are naturally violent or become that way due to human interference in the environment. Video provided by Newsy
Powered by NewsLook.com
Some Tobacco Farmers Thrive Amid Challenges

Some Tobacco Farmers Thrive Amid Challenges

AP (Sep. 16, 2014) — The South's tobacco country is surviving, and even thriving in some cases, as demand overseas keeps growers in the fields of one of America's oldest cash crops. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

AFP (Sep. 16, 2014) — Scientists say a female colossal squid weighing an estimated 350 kilograms (770 lbs) and thought to be only the second intact specimen ever found was carrying eggs when discovered in the Antarctic. Duration: 00:47 Video provided by AFP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) — Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
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:
from the past week

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