High-ranking females bias their investment in favour of male calves in captive Ammotragus lervia |
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Authors: | Jorge Cassinello |
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Institution: | (1) Estación Experimental de Zonas Aridas (CSIC), c/General Segura 1, 04001-Almería, Spain, ES |
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Abstract: | Calf suckling behaviour is a valid measure of maternal investment in the Saharan arrui, Ammotragus lervia sahariensis, since this variable is strongly correlated with the inter-birth interval. High-ranking females allocate their resources
preferentially towards their sons, as the average suckling rate is significantly higher in male calves than in female calves
during their 1st month of life, when maternal investment reaches the highest values of the whole lactation period. However,
average suckling-bout duration shows no sex differences. Some maternal behaviours, such as sniffing and licking, are strongly
correlated with suckling events. Only during the calves’ 1st week is the mother responsible for maintaining proximity; but
from the following week on the calves are mainly responsible for maintaining it. In addition, when the calves are 1 month
old, high-ranking females tend to maintain a stronger link with their male calves. Female calves spend more time with their
mothers than male calves during their 1st month of life, if the mother’s rank is lower than 60%; otherwise, the opposite occurs,
male calves being close to their mothers for longer, even from their 1st week of life. Finally, the higher the maternal rank
the higher the proportion of male calves delivered.
Received: 18 April 1995/Accepted after revision: 11 February 1996 |
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Keywords: | Ammotragus Ungulates Parental investment Sex ratio |
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