Camel Calves as Opportunistic Milk Thefts? The First Description of Allosuckling in Domestic Bactrian Camel (Camelus bactrianus)

Abstract

Allosuckling is a situation when a female nurses a non-filial offspring. It was described in various ungulate species; however for camels this is the first description of this behaviour. The aim of the study was to assess the occurrence of allosuckling in captive camels (Camelus bactrianus) and to test whether it can be explained as a ‘milk-theft’ (opportunistic behaviour of calves) or alternatively as an altruistic behaviour of females. During 2005 and 2007, nine camel females and ten calves in four zoological gardens in the Czech Republic were observed. In total, 373 sucking bouts were recorded, from which 32 were non-filial (the calf sucked from the non-maternal female). Allosuckling regularly appeared in captive camel herds. As predicted for the milk-theft explanation, the non-filial calves sucked more often in the lateral position and even did not suck in the antiparallel position at all. The non-filial calves preferably joined the filial calf when sucking but in five cases (15.6% of non-filial sucking bouts) the calves sucked from non-maternal dam without the presence of filial calf. We then expected the differences in terminations of sucking bouts by females but did not find any difference in sucking terminations for filial and non-filial calves. As the calves were getting older, the incidence of allosucking increased. This was probably because skills of the calf to outwit the non-maternal dam increased and/or the older calves might be more motivated for allosucking due to the weaning process. Finally, duration of a sucking bout was shorter with non-filial than filial calves. The results of the study support the hypothesis of ‘milk theft’, being mostly performed by calves behaving as opportunistic parasites, but we cannot reject certain level of altruism from the allonursing females or their increased degree of tolerance to non-filial calves.

Allosuckling in reindeer (Rangifer tarandus): Milk-theft, mismothering or kin selection?

“…In our study, the tendency for F reindeer calves to adopt the antiparallel position during bouts (89.3%) was consistent with previous studies, while NF calves adopted the parallel and perpendicular positions in 41.5% of bouts, which was not consistent with previous studies. The antiparallel position was generally adopted by F offspring in camels (62.2%) (Brandlová et al, 2013), fallow deer (100%) (Ekvall, 1998;Pélabon et al, 1998), guanacos (Zapata et al, 2009), cattle (approximately 70-90%) (Špinka and Illmann, 1992;Waltl et al, 1995) and red deer (100%) (Bartoš et al, 2001b). The perpendicular and parallel positions were generally adopted by NF calves in camels (100%) (Brandlová et al, 2013), fallow deer (56%) (Ekvall, 1998;Pélabon et al, 1998), cattle (approximately 53-85%) (Špinka and Illmann, 1992;Waltl et al, 1995) and guanacos (Zapata et al, 2009).…”

“…If allosuckling is driven by calves stealing milk, lactating females should reject NF offspring and may become aggressive towards NF offspring, and NF offspring should adopt the perpendicular or parallel positions to allosuckle, instead of the antiparallel position, to avoid being discriminated (Reiter et al, 1978;Zapata et al, 2009). Evidence for the milk-theft hypothesis has been reported, among other studies, in red deer (Cervus elaphus) (Landete-Castillejos et al, 2000), river buffalo (Bubalus bubalis) (Murphey et al, 1995), guanacos (Lama guanicoe) (Zapata et al, 2009), bactrian camels (Camelus bactrianus) (Brandlová et al, 2013), and multiparous Steller sea lions (Eumetopias jubatus) (Maniscalco et al, 2007). Offspring have been hypothesized to allosuckle due to misdirected maternal care, known as mismothering, suggesting no kin discrimination and kin recognition mechanisms.…”

“…Age of does was added as a covariate since it has been shown in fallow deer and bighorn sheep to be positively correlated with allosuckling (Ekvall, 1998;Hass, 1990). Because age of calf has been shown to increase the occurrence of allosuckling in calves of camels (Brandlová et al, 2013), fallow deer (Ekvall, 1998) and red deer (Landete-Castillejos et al, 2000), we controlled for this effect by including age of calf (in days) as a covariate in our model. Birth mass was added as a covariate, since calves of cattle cows (Víchová and Bartoš, 2005) and river buffalo (Paranhos da Costa et al, 2000) with low birth mass performed more allosuckling.…”

Evidence of Reciprocal Allonursing in Reindeer, Rangifer tarandus

“…The mean duration of allonursing bouts was 36.78 ± 65.47 s in bactrian camels (Brandlová et al. ), 0.9 ± 0.06 min in zebu (Das et al. ), 41.7 ± 8.7 s in fallow deer (Ekvall ), 67.52 ± 7.22 s in red deer (Drábková et al.…”

“…), fallow deer (Birgersson & Ekvall ), cows ( Bos taurus ) (Víchová & Bartoš ), bactrian camels ( Camelus bactrianus ) (Brandlová et al. ), zebras (Olléová et al. ) and big horn sheep (Hass ).…”