Herpetology Notes, volume 14: 225-227 (2021) (published online on 01 February 2021)

Mating in free-ranging Neotropical , durissus: Is it risky for males?

Selma Maria Almeida-Santos1,*, Thiago Santos2, and Luis Miguel Lobo1

Field observations of the mating behaviour of The male remained stretched out for about 20 minutes are scarce, probably because of the secretive nature and and showed no defensive posture even with the presence low encounter rates of many (Sasa and Curtis, of the observer. We then noticed drops of blood on the 2006). In the Neotropical , vegetation and the hemipenis (Fig. 1 E-F). We could not Linnaeus, 1758, mating has been reported only in determine the origin of the blood, but we suggest two captive individuals (Almeida-Santos et al., 1999). Here nonexclusive hypotheses. The hemipenis spicules may we describe the first record of the mating behaviour of have hurt the female’s vagina while she was dragging the the Neotropical rattlesnake, Crotalus durissus, in nature male over a long distance. Alternatively, the male may (Fig. 1 A). have suffered an injury to the hemipenis while being Observations were made on 9 March 2017, at 14:54 h, dragged quickly by the female. The slow hemipenis a warm and sunny day (temperature = 27.1 oC; relative retraction and the male’s fatigue after copulation may humidity = 66%), in an ecotone between dry forest and better support the second hypothesis. Cerrado (Brazilian savannah) in Prudente de Morais, Potential costs for male C. durissus during mating Minas Gerais, (-19.2841 °S,-44.0628 °W; datum season include increased activity and energy expenditure WGS 84). A male and a female C. durissus were in searching for oestrous females (Almeida-Santos et found copulating beneath a small pile of leaf litter in a al., 2004; Aldridge and Duvall, 1992) and male-male densely vegetated area near a pasture. The snakes were combat (Almeida-Santos et al., 1999). For female C. accidentally disturbed when the observer approached the durissus, which assume a passive posture in copulation, place where they were coiled. Consequently, the female energy expenditure may be lower, thus allowing them to attempted to flee, dragging the male for about 5 minutes flee as soon as the copulation ends. (Fig. 1 B-D). Copulation lasted about 20 minutes, but it The copulation reported here occurred in late summer, had already begun when the snakes were found. After which coincides with the peak of spermiogenesis and copulation, the male took about 20 minutes to retract sperm storage in the ductus deferentia (Almeida-Santos the hemipenis back into the base of the tail. Retraction et al., 2004). At that time, male C. durissus are actively of the hemipenis began by the calyces, which are searching for oestrous females (Almeida-Santos et al., pulled back into the tail by a contraction of the retractor 2004). The observed copulation coincides with the muscle (Dowling and Savage, 1960; Porto et al., 2013). timing of mating in North American Crotalus in late Retraction of the calyces lasted about 15 minutes, and summer and autumn (Aldridge and Duvall, 2002), the base of the hemipenis remained unchanged for about which corroborates a phylogenetic conservatism of 5 minutes until retracted into the tail (Fig. 1 E-F). mating season in the .

Acknowledgments. We thank Henrique Braz for suggestions and language editing. 1 Instituto Butantan, Laboratório de Ecologia e Evolução, Avenida Vital Brasil, 1500, Butantã, São Paulo, SP, 05503- References 900, Brazil. Aldridge, R.D., Duvall, D. (2002): Evolution of the mating season 2 Pontifícia Universidade Católica de Minas Gerais, Laboratório in the pitvipers of North America. Herpetol. Monographs 16: de Ecologia Evolutiva de Anfíbios e Répteis, Belo Horizonte, 1–25. MG, 30535-610, Brazil. Almeida-Santos, S.M., Laporta-Ferreira, I.L., Antoniazzi, M.M., * Corresponding author. E-mail: [email protected] Jared, C. (2004): Sperm storage in males of the Crotalus © 2021 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0. durissus terrificus (Crotalinae: ) in southeastern 226 Selma Maria Almeida-Santos et al.

Figure 1. Copulation of free-ranging Neotropical rattlesnakes, Crotalus durissus. (A) The couple (male on the left and female on the right) in copulation. Note the hemipenis inserted in the cloaca (circle). (B) The female (to the left), still in copula (circle), drag the male to the right (fine arrow). In (C) and (D), the female continues to drag the male to the left. (E) The chalices of hemipenes (Ch) are reversing. Note the hemipenis base (Ba) and blood in the vegetation (Bl). (F) The hemipenis base remains everted (Ba), blood can be seen on the vegetation (Bl).

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Accepted by Andrew Durso