Annual rhythm of body weight in Prezwalski horses
Publication Type: |
Journal Article |
Year of Publication: |
2003 |
Authors: |
Klaus M. Scheibe; Wolf J. Streich |
Publication/Journal: |
Biological Rhythm Research |
Keywords: |
adaptation, annual rhythm, body weight, equus ferus przewalskii, feeding, photoperiod, re-introduction, temperature |
Abstract:
The live-weight of female Przewalski horses in a semi-natural reserve has been recorded continuously over 6 years by means of an automatic weighing machine and automatic identification. Data were tested for cyclic as well as for linear trend effects and a mathematical model was developed. A clear annual rhythm of live-weight with the maximum in October was demonstrated. During the first 2 years of recording, the level of the annual rhythm was constant but, thereafter, different individual trends were found. Those individuals showing a steeply rising trend suffered from laminitis after three annual cycles. The periods of rising body weight corresponded to unusual mild winters. Animals newly introduced into the reserve from zoos showed a rise in their body weight in an adaptation phase. Furthermore, there was evidence for a phase adjustment of the annual rhythm. The results are discussed against a background of the theory of annual rhythms, and can be used as a basis for seasonal variations of feeding in zoos and for a re-evaluation of recommendations for population density in similar reserves. For reintroductions as well as for a transfer from zoos to semi-natural reserves, a longer adaptation phase is recommended.