Faithful fathers and crooked cannibals: the adaptive significance of parental care in the bush frog Raorchestes chalazodes, Western Ghats, India
Parental care has evolved many times in multiple taxa and, by definition, enhances offspring survivorship. Anurans exhibit a diverse array of parental care behaviors, but studies examining their adaptive significance in an evolutionary context are limited. The critically endangered bush frog, Raorchestes chalazodes (Rhacophoridae), only breeds inside hollow internodes of the endemic bamboo (Ochlandra travancorica) in the southern Western Ghats of India from June through October. From systematic surveys, we established that adult males are sole caregivers exhibiting egg attendance and egg guarding behavior. Predation was the main cause of egg mortality in the absence of an attending male; the majority of predation events were caused by conspecific males. The results highlight the role of regional and microhabitat-specific selection pressures such as strong seasonality, limited resources, and competition for oviposition sites. Oviposition sites are in high demand, but in short supply and by consuming unattended eggs, the conspecific male may benefit from nutritional gains as well as mating opportunities at the oviposition site. Our work lays foundations for further examination of social and reproductive behaviors of anurans not only in the Western Ghats but also in South and Southeast Asia.
The bamboo-breeding frog R. chalazodes is one among 62 arboreal frogs of the genus Raorchestes found in the Western Ghats of India. It was presumed extinct until its rediscovery in 2011 from within bamboo internodes endemic to the region. Adult males of this species care for direct developing eggs, laid exclusively inside of hollow bamboo internodes. Conspecific males cannibalized unattended egg clutches when the caregiving adult male was experimentally removed from the oviposition site. Eggs were also eaten by ants, parasitized by flies, and died from fungal infections or drowned. Male parental care in the form of egg attendance and egg guarding prevents predation of eggs and increases offspring survivorship. Parental care behavior is common among several taxa with external fertilization. Integrating natural history with in situ experiments may reveal novel insights into the adaptive nature of parental care behavior.
KeywordsReproductive ecology Parental care Predation Cannibalism Evolution The Western Ghats
The Tamil Nadu Forest Department provided permits, and their staff provided logistical support. Drs M. D. Soubadra, T. Ganesh, and R. Ganesan permitted the use of facilities of the Agastyamalai Community-based Conservation Centre, and M. Mathivanan, A. Saravanan, and the staff provided logistics. Dr. T. Ganesh, Dr. K.V. Gururaja, S. Johnson, A. Sachin, A. Saravanan, S. Tamizalagan, Vidisha Kulkarni, and Vignesh Kamath assisted KSS in data collection. KSS was supported the Navjot Sodhi Conservation Biology scholarship from the National University of Singapore. Field research was supported by The Mohamed bin Zayed Species Conservation Fund and Chicago Zoological Society-Endangered Species Fund. Dr. K.V. Gururaja provided critical inputs to KSS during fieldwork and when writing the manuscript. K. Vidisha prepared the illustration. This manuscript is also an outcome of the Science Writing workshop conducted by the Conservation Leadership Program in 2017, Bengaluru, India, and benefitted immensely from the inputs of Dr. Martin Fisher and Ms. Laura Owens. Dr. Frank Rheindt commented on the manuscript. Comments from Catharina Karlsson, Dr. Eva Ringler, and another anonymous reviewer improved the quality of this paper. We thank them all.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national (WL5(a) 19456), and/or institutional guidelines (B136072 and M140424) for the care and use of animals were followed.
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