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 July 31, 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 July 31, 2014).

Share This




More Plants & Animals News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Visitors Feel Part of the Pack at Wolf Preserve

Visitors Feel Part of the Pack at Wolf Preserve

AP (July 31, 2014) — Seacrest Wolf Preserve on the northern Florida panhandle allows more than 10,000 visitors each year to get up close and personal with Arctic and British Columbian Wolves. (July 31) Video provided by AP
Powered by NewsLook.com
Florida Panther Rebound Upsets Ranchers

Florida Panther Rebound Upsets Ranchers

AP (July 31, 2014) — With Florida's panther population rebounding, some ranchers complain the protected predators are once again killing their calves. (July 31) Video provided by AP
Powered by NewsLook.com
Dangerous Bacteria Kills One in Florida

Dangerous Bacteria Kills One in Florida

AP (July 31, 2014) — Sarasota County, Florida health officials have issued a warning against eating raw oysters and exposing open wounds to coastal and inland waters after a dangerous bacteria killed one person and made another sick. (July 31) Video provided by AP
Powered by NewsLook.com
Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) — Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) 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