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Food availability affects behavior but not circulating gonadal hormones in maternal Belding's ground squirrels
S Nunes1, E M Muecke, H E Ross
1Department of Biology, University of San Francisco, San Francisco, CA 94117-1080, USA. nunessco@msu.edu
Physiology & Behavior
|March 10, 2001
Summary
Steroid hormones like testosterone, progesterone, and estradiol influence maternal behaviors in ground squirrels. However, increased food availability did not alter hormone levels or behavioral patterns during reproduction.
Area of Science:
- Behavioral Endocrinology
- Reproductive Biology
- Animal Behavior
Background:
- Steroid hormones are implicated in regulating energy balance and reproductive behaviors.
- Understanding the role of hormones in maternal care is crucial for reproductive success.
Purpose of the Study:
- To investigate the influence of testosterone (T), progesterone (P), and estradiol (E2) on maternal behaviors in free-living female Belding's ground squirrels (Spermophilus beldingi).
- To examine the interaction between energy availability and hormonal regulation of reproductive behaviors.
Main Methods:
- Observation of female ground squirrel behavior throughout the reproductive cycle.
- Measurement of plasma concentrations of T, P, and E2.
- Experimental manipulation of food availability (provisioned vs. unprovisioned females).
Main Results:
- Hormone levels (T, P, E2) and their temporal patterns were similar between provisioned and unprovisioned females.
- Peaks in nest maintenance and aggression during gestation correlated with elevated T, P, and E2.
- Provisioned females exhibited higher rates of resting, vigilance, and aggression; unprovisioned females spent more time feeding and moving.
Conclusions:
- Gonadal steroids appear to mediate behaviors essential for establishing maternal territories and nests.
- Increased energy availability does not alter hormone concentrations or behavioral timing in maternal ground squirrels.
- Hormonal regulation of maternal behavior is distinct from the direct energetic regulation of behavior.
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