Social dominance of female red deer (Cervus elaphus): the effect of lactation, age and sex hormones
Social status can significantly influence reproductive fitness in a number of mammal species. However, mechanisms that affect social status in female mammals were rather neglected so far. Therefore, we examined the potential effect of lactation, age, body mass and selected sex hormones (testosterone [T], estradiol [E2], progesterone [P], FSH and LH) on social status in 33 female red deer (Cervus elaphus; IAS, Prague, Podlesko) during five seasons. We studied 84 milk and 15 yeld hinds. Social status of the female was assessed using the David score (David 1987, Biometrika 74: 432). We assumed that social status will be higher: (1) in milk than in yeld hinds; (2) in older than in younger hinds; (3) in heavier than in lighter hinds; and (4) in hinds with higher levels of sex hormones. As we expected, (1) milk hinds were more dominant than yeld hinds (milk: 7.53 ± 4.68; yeld: -41.67 ± 13.11; p < 0.0001), and (2) social status of the female increased with her increasing age (milk: p < 0.0001; yeld: p < 0.03). Body mass of the female did not affect her social status (NS). We did not found the positive effect of sex hormones that we expected. On the contrary, we found that: (a) the social status of milk hind increased with the decreasing level of T (p < 0.01); while (b) the social status of yeld hind increased with the decreasing level of LH (p < 0.01). We also observed that T levels decreased with the increasing age of milk hinds (p < 0.0001) and LH levels did not change according to the age of the yeld hinds (NS). Hence, lactation and age seem to play key roles in social relationships of female red deer. A general assumption of the positive effect of sex hormones on social status in female mammals was not supported.
Dušek Adam, RNDr., Ph.D.
Jiříková Kamila, Ing.
Esattore Bruno, MSc.
Kotrba Radim, Ing., Ph.D.
Kott Tomáš Ing. Ph.D.
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