Thermal physiology and activity in relation to reproductive status and sex in a free-ranging semelparous marsupial

Abstract

In a changing climate, southern hemisphere mammals are predicted to face rising temperatures and aridity, resulting in food and water shortages, which may further challenge already constrained energetic demands. Especially semelparous mammals may be threatened because survival of the entire population depends on the success of a single breeding event. One of these species, the yellow-footed antechinus, Antechinus flavipes, a small, heterothermic marsupial mammal, commences reproduction during winter, when insect prey is limited and energetic constraints are high. We examined the inter-relations between thermal and foraging biology of free-ranging A. flavipes and examined whether they use torpor for energy conservation, despite the fact that reproduction and torpor are considered to be incompatible for many mammals. Females used torpor during the reproductive season, but patterns changed with reproductive status. Prior to breeding, females used frequent (86% of days), deep and long torpor that was more pronounced than any other reproductive group, including pre-mating males (64% of days). Pregnant females continued to use torpor, albeit torpor was less frequent (28% of days) and significantly shorter and shallower than before breeding. Parturient and lactating females did not express torpor. During the mating period, males reduced torpor use (24% of days). Pre-reproductive females and pre-mating males were the least active and may use torpor to minimize predator exposure and enhance fat deposition in anticipation of the energetic demands associated with impending mating, gestation and lactation. Reproductive females were most active and likely foraged and fed to promote growth and development of young. Our data show that A. flavipes are balancing energetic demands during the reproductive season by modifying torpor and activity patterns. As the timing of reproduction is fixed for this genus, it is probable that climate change will render these behavioural and physiological adaptations as inadequate and threaten this and other semelparous species.

Growing Up in a Changing Climate: How Temperature Affects the Development of Morphological, Behavioral and Physiological Traits of a Marsupial Mammal

“…Extensive reviews on Bergmann's rule have found mixed support for temperature being the main factor influencing body size in mammals, and have suggested that other factors such as food availability are more important (Alhajeri and Steppan, 2016;Gohli and Voje, 2016). As antechinus are known to increase torpor use when exposed to cold conditions to save energy (Geiser, 1988;Parker et al, 2019), it is likely that they increased torpor use when exposed to the cold treatment. Therefore, this strategy, along with changes in activity patterns, may reduce body mass loss under cold conditions and explain why there was no difference between the treatment groups in our study.…”

Seasonal Expression of Avian and Mammalian Daily Torpor and Hibernation: Not a Simple Summer-Winter Affair†

“…Food withdrawal increased daily torpor expression to about 30-80% from autumn to spring when juveniles are excluded, which did express torpor in summer (Geiser, 1988). In the field, A. flavipes expressed torpor in winter, but torpor patterns were strongly affected by reproductive status (Parker et al, 2019), whereas in A. stuartii, daily torpor in winter was mainly affected by weather (Hume et al, 2020).…”

“…Andean Hillstar, Oreotrochilus estella, spring and autumn unknown (Carpenter, 1974) Rufous hummingbird, Selasphorus rufus, migratory, winter unknown (Hiebert, 1993) Sunbird, Nectarina famosa, summer (Downs and Brown, 2002) Black-capped chickadee, Poecile atricapilla, spring and autumn unknown (Sharbaugh, 2001) Fat-tailed dunnart, Sminthopsis crassicaudata (Geiser and Baudinette, 1987;Warnecke et al, 2008) Stripe-faced dunnart, Sminthopsis macroura (Geiser and Baudinette, 1987;Körtner and Geiser, 2009) Kowari, Dasyuroides byrnei (Geiser and Baudinette, 1987) Blossom-bat, Syconycteris australis (Geiser et al, 1996;Coburn and Geiser, 1998) Elephant shrew, Elephantulus myurus (Mzilikazi and Lovegrove, 2004) White-footed mouse, Peromyscus leucopus (Lynch et al, 1978) Deer mouse, Peromyscus maniculatus (Tannenbaum and Pivorun, 1989) Desert hamster, Phodopus roborovskii (Chi et al, 2016;Geiser et al, 2019) Spiny mouse, Acomys russatus (Levy et al, 2011) Autumn to spring Tawny frogmouth, Podargus strigoides (Körtner et al, 2001) Owlet-nightjar, Aegotheles cristatus (Brigham et al, 2000) Whip-poorwill, Caprimulgus vociferous, migratory, winter unknown (Lane et al, 2004) Noisy miner, Manorina melanocephala (Geiser, 2019) Brown antechinus, Antechinus stuartii (Geiser, 1988;Hume et al, 2020) Yellow-footed antechinus, Antechinus flavipes (Geiser, 1988;Parker et al, 2019) Sugar glider, Petaurus breviceps (Körtner and Geiser, 2000a;Nowack et al, 2015) Djungarian hamster, Phodopus sungorus (Heldmaier and Steinlechner, 1981) other aspect of seasonal torpor use, the control of its expression differs among species and revealing the responsible cues will require further work.…”

Red‐tailed phascogales: A review of their biology and importance as model marsupial species

“…No other animals (six males and four females) entered torpor with all other animals maintaining a T b between 29.9°C and 39.8°C (Stannard et al, unpublished). Torpor has been used by other semelparous dasyurid marsupials more frequently after wildfires, during pregnancy and to avoid unfavorable weather conditions (Hume et al, 2020; Matthews et al, 2017; Parker et al, 2019). Thus torpor is important for survival as an energy saving mechanism, and additionally using torpor allows them to avoid predators.…”