Evidence of Reciprocal Allonursing in Reindeer, Rangifer tarandus

Abstract

The nursing of non‐offspring is referred to as allonursing. Reciprocity is a hypothesized cause of allonursing, but previous studies have not strongly supported or found no evidence in support for this hypothesis. Biological market theory was applied to 25 reindeer (Rangifer tarandus) does and their calves to investigate allonursing reciprocity across bouts and within dyads and assess the diversity of allonursing partners. We also investigated whether variation in allonursing would be associated to relatedness within dyads. We recorded both the occurrence and the duration of 1027 successful allonursing solicitations. All does allonursed, and only three of the 25 calves were not observed being allonursed. Throughout the study, 234 allonursing dyadic pairs were observed. Does allonursed the calves of several does, but allonursing was not distributed evenly among all potential partners. Twenty does were members of at least 1 dyad with a high degree of reciprocity based on the number of allonursing bouts exchanged within the dyad. We found evidence of both relative and absolute allonursing reciprocity at the group level. Across bouts and within dyads, the reciprocal allonursing indexes varied greatly both for frequency and for duration, with an average tendency towards unidirectionality. Evidence of strong reciprocity within dyads was found in 32 dyads for number of allonursing bouts and in 25 dyads for duration of allonursing bouts. Across bouts and within dyads, the number of allonursing bouts received was not influenced by relatedness, allonursing bouts given or absolute rank difference. Allonursing was not interchanged for rank‐related benefits. Our results provide evidence of reciprocal allonursing at the group level, across bouts and within dyads, and reciprocal allonursing among chosen partners. Our results point to the usefulness of applying the biological market theory to allonursing and of considering allonursing as a tradable commodity, traded for itself, among chosen partners.

Effect of nursing behaviour, sex of the calf, and parity order on milk production of buffaloes

“…Some non-mutually exclusive hypotheses have been proposed to explain why lactating females nurse alien offspring: misdirected parental care (Packer et al, 1992), reciprocity (Ekvall, 1998;Engelhardt et al, 2015;Glonekov et al, 2016), kin selection (Pusey and Packer, 1994;Ekvall, 1998;Eberle and Kappeler, 2006;Engelhardt et al, 2016), evacuation of leftover milk (Riedman and Le Boeuf, 1982;Wilkinson, 1992), inexperience of females (Murphey et al, 1991;1995), and milk theft (Murphey et al, 1995;Maniscalco et al, 2007;Zapata et al,2009;Engelhardt et al, 2014;Glonekov et al, 2016).…”

Working dogs cooperate among one another by generalised reciprocity

“…Individuals must remember with whom they interacted before, and how a particular social partner behaved towards them in previous interactions 3 . Evidence for direct reciprocity among animals exists both from observations in nature and from experimental studies 6 7 8 9 10 11 12 13 , reviewed in refs 14 , 15 , 16 , 17 , 18 . In contrast to direct reciprocity, generalised reciprocity implies that individuals help others if they received help from someone else.…”

Further behavioural parameters support reciprocity and milk theft as explanations for giraffe allonursing

“…In this study, it was found that giraffe allonursed non-filial calves reciprocally, further supporting the reciprocity hypothesis as the primary explanation for allonursing amongst captive giraffe. While this hypothesis did not receive much support in the past 13 , recent studies involving ungulates provided evidence in support of reciprocity, explained by allosuckling ( Equus grevyi 32 ; Rangifer tarandus 28 ; Giraffa camelopardalis 19 , Bison bison 29 ). The current study revealed that allosuckling frequencies and time devoted to allosuckling increased concomitantly in dyad A and dyad B, corresponding with the reciprocity hypothesis which assumes that two females achieve higher fitness when nursing each other's offspring.…”