Summary
1. Global warming is rapidly emerging as a universal threat that could
alter the distribution of many animal species and change their
morphology, physiology, behavior and life history. The heat dissipation
limitation (HDL) hypothesis proposes that females’ reproductive
performance is limited by their capacity to dissipate heat. Although
exposure to wind is known to increase heat exchange, its effect on
reproductive performance is unknown.
2. In this study, the effect of simulated wind on the energy budget and
milk energy output of female striped hamsters (Cricetulus
barabensis ) was measured under cool (21°C) and hot (32.5°C) ambient
temperatures and the preference of hamsters for windy conditions in
lactating females was tested both in the laboratory and the wild.
3. Females lactating at 32.5°C significantly decreased their energy
intake and milk output, and raised lighter offspring than those
lactating at 21°C. Exposure to wind significantly increased both energy
intake during lactation and heat loss at both temperatures. Females
lactating at 32.5°C considerably increased their reproductive output
when exposed to wind. Moreover, females kept at an ambient temperature
of 21°C preferred sheltered conditions whereas those kept at 32.5°C
preferred exposure to simulated wind. We captured significantly more
lactating female hamsters on windy days in summer and on calm days in
spring. Wrapping a glass vessel in the fresh pelt of a striped hamster
significantly reduced the rate of both water loss and cooling.
4. These findings support the HDL hypothesis; high ambient temperatures
do appear to limit the energy intake and reproductive output of
lactating hamsters. Small mammals lactating under hot conditions may be
able to utilize the cooling properties of wind to increase their energy
intake and milk production, and thereby their reproductive output and
fitness.
Key-words: hot temperature; litter size; preference to wind;
reproductive output; striped hamsters