title: Field energetics of free-living, lactating and non-lactating echidnas (Tachyglossus aculeatus).
abstract: We measured daily energy expenditure (DEE) and water turnover rates in lactating and non-lactating short beaked echidnas (Tachyglossus aculeatus) using the doubly labelled water technique during the lactation period in spring. Reproductively inactive echidnas were on average significantly heavier (median: 3354 g; range: 2929-3780 g; N=4) than lactating females (median: 2695 g; range: 2690-2715 g; N=3) during the equivalent time period. The median water flux rate of lactating echidnas (152 ml day(-1); range: 120-198 ml day(-1)) did not differ significantly from that of non-lactating females (170 ml day(-1); range: 128-227 ml day(-1)). The median DEE of echidnas that were lactating was 645 kJ day(-1) (range: 581-850 kJ day(-1)), which was not different from the median DEE of non-reproductive control females (763 kJ day(-1); range: 720-766 kJ day(-1)). Lactating females somehow compensate for the energy costs of milk production, resulting in a daily energy budget that is not different from that of non-reproductive females. At least part of their energy minimising strategy could involve the use of moderate heterothermy, allowing a greater proportion of daily energy expenditure to diverted to milk production.
authors.affiliation: Department of Experimental Ecology, University of Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany. jutta.schmid@biologie.uni-ulm.de
authors.forename: Jutta
authors.initials: J
authors.lastname: Schmid
authors.forename: Niels A
authors.initials: NA
authors.lastname: Andersen
authors.forename: John R
authors.initials: JR
authors.lastname: Speakman
authors.forename: Stewart C
authors.initials: SC
authors.lastname: Nicol
mesh_terms: D000818:Animals; D001823:Body Composition; D001831:Body Temperature; D001835:Body Weight; D005260:Female; D007774:Lactation; D010987:Platypus / Q000033:anatomy & histology / Q000502:physiology*; D013648:Tasmania; D013997:Time Factors; D014867:Water
chemical_list: D014867:Water