Improved homeothermy and hypothermia in African lions during gestation

Abstract

Mammals use endogenously produced heat to maintain a high and relatively constant core body temperature (T b ). How they regulate their T b during reproduction might inform us as to what thermal conditions are necessary for optimal development of offspring. However, few studies have measured T b in free-ranging animals for sufficient periods of time to encounter reproductive events. We measured T b continuously in six free-ranging adult female African lions (Panthera leo) for approximately 1 year. Lions reduced the 24 h amplitude of T b by about 25% during gestation and decreased mean 24 h T b by 1.3 + 0.18C over the course of the gestation, reducing incidences of hyperthermia (T b . 39.58C). The observation of improved homeothermy during reproduction may support the parental care model (PCM) for the evolution of endothermy, which postulates that endothermy arose in birds and mammals as a consequence of more general selection for parental care. According to the PCM, endothermy arose because it enabled parents to better control incubation temperature, leading to rapid growth and development of offspring and thus to fitness benefits for the parents. Whether the precision of T b regulation in pregnant lions, and consequently their reproductive success, will be influenced by changing environmental conditions, particularly hotter and drier periods associated with climate change, remains to be determined.

On the interplay between hypothermia and reproduction in a high arctic ungulate

“…Few studies have examined the interplay between reproduction and body temperature variability in large, wild mammals. For example, pregnant African lions (Panthera leo) lower and stabilize their body temperature (hereafter T b ) to avoid episodes of hyperthermy 10 , and wolverines (Gulo gulo) 11 also lower their T b during pregnancy despite living in cold environments, whereas hibernating bears exhibit a high degree of homeothermy during pregnancy 12,13 . Also Svalbard reindeer (Rangifer tarandus platyrhynchus) lower their T b in winter, and some differences in T b patterns between reproductive and non-reproductive reindeer has been reported 5 , but the linkage between T b and reproductive status remains unclear.…”

Effects of reproduction and environmental factors on body temperature and activity patterns of wolverines

“…Moreover, we found that the pattern of daily mean T b of female wolverines differed between reproductive states, as reproductive females had significantly lower T b from day 12–81 than non-reproducing females. Decreased T b during gestation has been described in both domestic [20, 21] and wild mammals [5, 22, 68, 69]. Decreasing T b during gestation in pregnant female brown bears is presumably caused by changes in progesterone levels, with maximum progesterone levels during implantation, followed by a decrease during gestation.…”

“…Decreasing T b during gestation in pregnant female brown bears is presumably caused by changes in progesterone levels, with maximum progesterone levels during implantation, followed by a decrease during gestation. Maintaining stable T b during gestation and reducing maternal T b may minimize hyperthermia events, which promotes fetal development [22]. Fetal T b has been found to be dependent on and approximately 0.6 °C higher than maternal T b [21].…”

“…This is expected to be present under natural conditions as well. For instance, pregnant female lions ( Panthera leo ) exhibit gestational hypothermia and decrease their T b by 1.3 °C during gestation [22].…”

Heart rate sensor validation and seasonal and diurnal variation of body temperature and heart rate in domestic sheep

“…Technology development in bio-sensors enables measurement of a set of physiological traits, helping to assess the allostatic load and possibly define its stressors ( Wikelski and Cooke, 2006 ). Heart rate (HR) and body temperature (T b ) have been used to detect disease ( Marais et al., 2013 ), stress ( Evans et al., 2016 ), gestation and parturition ( Friebe et al., 2014 ; Trethowan et al., 2016 ; Thiel et al, 2019 ) and estrus ( Andersson et al., 2016 ) in free ranging terrestrial mammals and production animals. In many species, oxygen consumption and HR are closely related and although calibration is needed, HR can be used as a proxy for metabolic rate ( Green, 2011 ).…”