Late development of homoeothermy in mink (Mustela vison) kits – a strategy for maximum survival rate*

Abstract

The objective of this study was to establish the age at which mink kits develop functional homoeothermy. The investigation was based on the hypothesis that in this species with very immature neonates, late development of homoeothermy may be an adaptation to economize with energy. Measurements of heat production (HE) by means of indirect calorimetry lasting 3 h were performed on neonatal kits and kits from 1 to 54 days of age. Both single kits and groups of 4-5 huddling kits were kept at 15 degrees C (L) or 30 degrees C (H) [from 35 days onwards at 25 degrees C (H)]. Animals were weighed before and after the experiments and evaporative water losses (EWL) were calculated. When exposed to L temperature, single kits responded with a very low HE until 29 days of age, and groups of kits until 14 days of age. It was not until they reached an age of approximately 6 weeks that single kits showed a clear thermoregulatory response to the L temperature by increased HE, whereas groups of kits showed increased HE from 29th day onwards. When kept at H temperature, HE was low initially, but all kits showed elevated HE at 8 days of age, and the metabolic rate was similar for single kits and kits huddling in groups. Evaporative water losses was higher among single than among groups of kits and slightly lower but more variable for animals at L than at H temperature. It was concluded that mink kits develop functional homoeothermy at an age of close to 6 weeks and that the failure of very young kits to thermoregulate is an adaptation mechanism in order to economise with their very limited body energy reserves.

Maternal behaviour in American mink females with different behavioural profiles

“…Young mink are unable to maintain the proper body temperature up to 22-29 days after birth (Harjunpää and Rouvinen-Watt, 2004). The huddling effect can last up to 14 days or even up to 30 days after birth depending on many factors, e.g., environmental conditions, litter size, access to feed (Tauson et al, 2006). Only after that time, kits open their eyes (Brandt et al, 2013) and start to separate themselves from the siblings in the same nest.…”

“…The care of offspring after the birth and the lactation period play an important role in the life of young mink as these factors affect offspring growth and development (Newberry and Swanson, 2008). The survival of young animals directly depends on the involvement of the dams in care as well as environmental conditions (temperature, design) prevailing in the nest (Tauson et al, 2006;Malmkvist et al, 2007;Zschille et al, 2010). The time the female spends for the care of the young is important not only from ABSTRACT.…”

Pre-slaughter bodyweight and daily gains in mink are independent of the housing system

“…However, larger space and low density of animals might result in increased use of energy for maintaining sufficient body temperature compared with those mink that were kept in single-storey cages, where animals remained in close contact. According to Tauson et al (2006), mink kept in groups, that is, in higher density, accumulated less subcutaneous fat than those kept in pairs, since they did not need to use so much energy to maintain proper body temperature. The in-house research indicated only slight differences in bodyweight gains.…”

High ambient temperatures induce aggregations of chimney swifts Chaetura pelagica inside a roost

“…The closer huddling we observed at higher ambient temperatures could be a function of swifts trying to reduce evaporative water loss. At higher temperatures, the use of sheltered roosts (Bakken et al 1991) and huddling have been observed to reduce evaporative water loss in many taxa (Tauson et al 2006, Boratynski et al 2015. However, we did not measure water balances in swifts and this remains an area worth exploring in further study.…”