Scientists explore hormone evolution

Mar 03, 2009
A Kangaroo Rat in the wild.

(PhysOrg.com) -- New research techniques on animals living in the wild are helping scientists test long-held ideas about the role of hormones in survival, according to comments by Professor of Biology Jan Randall at the recent American Association for the Advancement of Science annual meeting.

Randall described recent developments in non-invasive techniques such as tracking mammals to gather feces, and sensitive tests that allow researchers to examine hormones in feces to formulate a more complete picture of the relationships among behavior, social systems and hormone function in mammals in the wild. "Previously, much of the information we have on hormones came from limited sets of models like lab rats and mice," Randall said. "This non-invasive method is allowing us to ask evolutionary, physiological questions about animals in the wild in completely new ways."

While most of the recent field research has been conducted on rodents, researchers are beginning to conduct field work with whales, predatory animals and other mammals. Randall said it's important to challenge findings discovered in a lab setting. "We see species specific adaptation of control systems so we must rethink our evolutionary models of hormones," she said. "As we discover more in the field, we may discover many more unusual adaptations important for reproduction and survival."

When Randall began post-doc work in the late 1970s, research was confined to drawing hormones from blood or from trapping animals in the wild. Often, those methods yielded hormone samples that were tainted by heightened stress hormones when the animals were handled by researchers. If researchers can identify which specific animal produced feces in the wild, it's possible to gain a better understanding of the effects of social stress and survival. "We need a specific sample and a social context to know what's going on hormonally," Randall said.

To study stress in natural populations, Randall collected feces from the great gerbil, Rhombomys opimus, in Uzbekistan over the course of six years, and the giant kangaroo rat, Dipodomys ingens, in California. The great gerbils are highly social rodents who live in high density communities. Some male gerbils would live with up to six females and their offspring. Randall wanted to know whether the social stress was affecting the male's ability to survive. For six years, Randall and her collaborators collected feces from specific males at various times throughout the year and found that males were stressed in large family groups but that outside factors like drought had a greater influence on survival than stress.

Randall and her graduate student, Julia Barfield, collected fecal samples during the breeding and non-breeding cycles of the giant kangaroo rat. They found significantly higher levels of testosterone in the summer non-breeding season than in the breeding season in both male and female kangaroo rats, which counters previous research conducted in a laboratory setting. Randall said the finding illustrates the flexibility of hormonal control systems and the importance of exploring them in wild populations.

Provided by San Francisco State University

Explore further: Human sense of fairness evolved to favor long-term cooperation

add to favorites email to friend print save as pdf

Related Stories

Alibaba's plan: Today, China. Tomorrow, the world.

14 minutes ago

Amazon and eBay should watch their backs. As Chinese e-commerce powerhouse Alibaba readies what could be the biggest initial public offering ever on the New York Stock Exchange, it is quietly hinting at plans ...

Stem cells use 'first aid kits' to repair damage

14 minutes ago

Stem cells hold great promise as a means of repairing cells in conditions such as multiple sclerosis, stroke or injuries of the spinal cord because they have the ability to develop into almost any cell type. ...

Last month was hottest August since 1880

18 minutes ago

Last month was the hottest August on record for global average temperatures over land and ocean surfaces, the US National Oceanic and Atmospheric Administration said on Thursday.

First eyewitness accounts of mystery volcanic eruption

28 minutes ago

New light has been shed on one of the biggest volcanic eruptions in the last 500 years—the so-called 'Unknown eruption'—thanks to an unusual collaboration between a historian and a team of earth scientists at the University ...

Recommended for you

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Bren
not rated yet Mar 04, 2009
That is interesting. Isnt a bad thing to look at. Any information is good to have.