Evolved changes in maternal care in high-altitude native deer mice [RESEARCH ARTICLE]

Cayleih E. Robertson and Grant B. McClelland At high altitude (HA), unremitting low oxygen and persistent cold push small mammals close to their metabolic ceilings, leaving limited scope for aerobically demanding activities. However, HA breeding seasons are relatively short and endemic rodents compensate with larger litters than low altitude (LA) conspecifics. Rodent mothers are the sole source of heat and nutrition for altricial offspring and lactation is energetically costly. Thus, it is unclear how HA females balance energy allocation during the nursing period. We hypothesized HA female rodents invest heavily in each litter to ensure postnatal survival. We measured maternal energetic output and behavior in nursing deer mice (Peromyscus maniculatus) native to LA (400m a.s.l.) and HA (4350m a.s.l.) under control (24oC, 760mmHg) and cold hypoxia (CH) conditions, simulating HA (5oC, 430mmHg). Strikingly, resting metabolic rates of lactating HA and LA females under CH were 70% to 85% of their maximal aerobic capacity. In CH, LA mothers increased both nursing time and milk fat content, however their pups were leaner and severely growth restricted at weaning. HA mothers also increased nursing in CH but for far less time than LA mothers. Despite receiving less care, HA pups in CH only experienced small growth restrictions at weaning and maintained body composition. As adults, HA mice raised in CH had increased aerobic capacity compared to controls. These data suggest that HA mothe...
Source: Journal of Experimental Biology - Category: Biology Authors: Tags: RESEARCH ARTICLE Source Type: research