9th International Deer Biology Congress

AUTHORS: Jitka Bartosova, Ludek Bartos, Dominika Formanova-Vankova, Jorga Drabkova, Ludmila Svecova, Adam Dusek, Jan Pluhacek, and Radim Kotrba – Institute of Animal Science

ABSTRACT: Females of many ungulate species, including red deer hinds, often nurse non-filial offspring. Causes of such at first sight strange and non-economical investment are not yet fully understood and seem to differ among species. Across studies, large individual variability in the incidence of allonursing has been reported. Allosuckling has been discussed as an artefact caused by unnatural breeding conditions or reproductive errors on farms (e.g., lack of maternal experience, misdirected maternal care, may be combined with “milk thieving” by the infant). On the other hand, allosuckling may be explained from evolutionary perspective in terms of altruism that evolved either through kin selection, or through reciprocity (or another mechanism) in small stable social groups. Allonursing females could thus help balance growth deficiencies of their (related) herd mates’ progeny.
We tested hypothesis of compensatory function of allosuckling in farmed red deer. The predictions were (i) through allosuckling calves compensate their growth and/or maternal nutrient insufficiencies; (ii) nursing of non-filial calves does not negatively affect maternal care provided to filial calves, as well as their growth; (iii) allosucking calf should not find an energy demanding tactic get non-maternal milk; and (iv) red deer hinds discriminate young they nurse (allonursing is not accidental or random).
From 3952 suckling bouts recorded in a group of red deer, 13.5% were non-filial. Nursing non-filial calves did not mean failure of maternal care provided to filial calves. Neither growth rate nor weaning weight of calves was affected by allonursing behavior of the mother. Calves sucking beside mothers also non-maternal females grew less and were lighter at weaning, and were also less successful in sucking the mother. Despite large individual variance in dams’ allonursing incidence, allosucking calves had well chance (more to 70%) to be nursed when solicited, without use any special tactic. Variability in calves’ allosucking behavior reflected their actual needs, and allonursing behavior of the dams seemed to reflect their possibilities above maternal investment. As presumed, nursings were not equally distributed among the calves, occurring most frequently within filial pairs. The hinds nursed filial calves almost 3times more frequently than non-filial calves when being solicited. Two types of non-filial allosuckers were detected, “preferred” (suckling mostly accepted by the particular hind) and “non-preferred” (suckling mostly rejected). Preferred non-filial calves had even higher success to be nursed than filial calves (P