Temporal and Spatial Complexity of Maternal Thermoregulation in Tropical Pythons

Abstract

Parental care is a widespread adaptation that evolved independently in a broad range of taxa. Although the dynamics by which two parents meet the developmental needs of offspring are well studied in birds, we lack understanding about the temporal and spatial complexity of parental care in taxa exhibiting female-only care, the predominant mode of parental care. Thus, we examined the behavioral and physiological mechanisms by which female water pythons Liasis fuscus meet a widespread developmental need (thermoregulation) in a natural setting. Although female L. fuscus were not facultatively thermogenic, they did use behaviors on multiple spatial scales (e.g., shifts in egg-brooding postures and surface activity patterns) to balance the thermal needs of their offspring throughout reproduction (gravidity and egg brooding). Maternal behaviors in L. fuscus varied by stage within reproduction and were mediated by interindividual variation in body size and fecundity. Female pythons with relatively larger clutch sizes were cooler during egg brooding, suggesting a trade-off between reproductive quantity (size of clutch) and quality (developmental temperature). In nature, caregiving parents of all taxa must navigate both extrinsic factors (temporal and spatial complexity) and intrinsic factors (body size and fecundity) to meet the needs of their offspring. Our study used a comprehensive approach that can be used as a general template for future research examining the dynamics by which parents meet other developmental needs (e.g., predation risk or energy balance).

The consequences of alternative parental care tactics in free‐ranging pythons in tropical Australia

“…Undoubtedly, egg production comprised the largest energetic investment by females in our study, but increased T body during reproduction may have also contributed to the energetic costs. Because L. fuscus surface activity is minimal during reproduction (particularly during brooding), female L. fuscus are aphagic during reproduction (Madsen & Shine 1999), and L. fuscus T body conforms to ambient temperature (females are non-thermogenic: Stahlschmidt et al 2012), actual metabolic rate likely approximated standard metabolic rate of females in our study. On the basis of Bedford & Christian's (1998) data, the shift that we documented in T body would have increased maternal energy expenditure (standard metabolic rate) by 14% and 27% during gravidity and egg brooding, respectively.…”

“…The scientific literature on parental care has been dominated by studies on mammals and birds (Clutton-Brock 1991;Stahlschmidt 2011), but reptiles also offer excellent model systems for analysis of this topic (Shine 1988). In particular, pythons have emerged as a useful taxon for studying the benefits, costs and trade-offs of parental care (reviewed in Stahlschmidt & DeNardo 2011). The family Pythonidae exhibits female-only parental care, the predominant mode of care when considering all animal taxa (Gross & Shine 1981;Zeh & Smith 1985;Clutton-Brock 1991).…”

“…During egg retention (gravidity), at oviposition (nest-site selection) and throughout incubation (egg brooding), female pythons also improve the thermal developmental environment, which strongly influences fitness-related variables in offspring (e.g. developmental rate, body size, locomotion and behaviour) (Vinegar, Hutchison & Dowling 1970;Shine et al 1997;Madsen & Shine 1999;Lourdais, Heulin & DeNardo 2008;Stahlschmidt, Brashears & DeNardo 2011a;Stahlschmidt & DeNardo 2011). However, parental care in pythons is costly to females in terms of survival and reproductive output (Madsen & Shine 1999) and in reduced body condition (Madsen & Shine 1999; but see Aubret et al 2005).…”

Facultative thermogenesis during brooding is not the norm among pythons

“…The two species with confirmed facultative thermogenesis are in the different clades-P. molurus within the Afro-Asian group and M. spilota within the Indo-Australian group. Conversely, both primary clades are also known to contain species where the absence of facultative thermogenesis has been confirmed-the rock python (P. sebae) (Vinegar et al 1970) and the ball python (P. regius) (Ellis and Chappell 1987) within the Afro-Asian clade and the reticulated python (P. reticulatus) (Vinegar et al 1970), the water python (Liasis fuscus) (Stahlschmidt et al 2012), and the Children's python (Antaresia childreni) (Stahlschmidt and DeNardo 2009) in the Indo-Australian clade (Fig. 1).…”