N1 2015 Northeastern Naturalist Notes Vol. 22, No. 1 C.F. Smith and G.W Schuett Putative pair-bonding in Agkistrodon contortrix (Copperhead) Charles F. Smith1, 2, 4,* and Gordon W Schuett1, 3, 4 Abstract - Pair-bonding between sexes is common in vertebrate taxa, yet it has been noted far less frequently in some groups such as reptiles, and snakes in particular. Evidence to date indicates that many snake mating-systems are polyandrous, with both males and females having multiple partners in a single breeding season, and thus unlikely to exhibit lengthy pair-bonds. Wittenberger and Tilson (1980) suggested that pair-bonding exists when pairs remain intact for a consecutive period equaling at least 25% of the breeding season. Using this criterion, we present evidence of pair-bond formation in a North American pitviper, Agkistrodon contortrix (Copperhead), a species with a polyandrous mating system. Pair-bonding during all phases of reproduction (PBR) is common in birds (Lack 1968, Yezerinac et al. 1995), and in other vertebrate lineages, especially where biparental care is present (Black 1996, Mathews 2002). However, it has been documented much less often in other groups, such as reptiles (Harrison 2013, O’Connor and Shine 2003), and snakes in particular (Black 1996, Clutton-Brock 1989, Dobson et al. 2010, Fricke 1986), which may be due to difficulty with documenting PBR rather than to rarity. In animals that form PBRs, it was once assumed that male–female partners were parents to all offspring (Bull 2000, Bull et al. 1998), yet extra-pair copulations (EPCs) and multiple paternity have been documented in many bird species, even those showing life-long pair-bonding (Ardern et al. 1997; Birkhead and Møller 1992, 1996; Lifjeld et al. 1993; Petrie et al. 1998; Westneat 1990; Yamagishi et al. 1992), as well as in mammals (Palombit 1994; Reichard 1995; Soulsbury 2010). Evidence to date supports the view that many snakes are polyandrous (Clark et al. 2014, Duvall et al. 1992, Rivas and Burghardt 2005, Shuster and Wade 2003), and both males and females have multiple sex partners within a single breeding season. This mating- system type suggests that pair-bonding for the purpose of mating or mate guarding may not be common. However, in an insular population of Agkistrodon piscivorus Lacepede (Cottonmouth) on Sea Horse Key, FL, long-term (weeks-long) association of male– female pairs is common (H.B. Lillywhite, University of Florida, Gainesville, FL, pers. comm.; Wharton 1966). Continuous long-term male–female associations have also been documented in Crotalus atrox Baird & Girard (Western Diamond-backed Rattlesnake) (Clark et al. 2014) and Crotalus molossus Baird & Girard (Black-tailed Rattlesnake) (Persons et al., in press). In both species, pair-associations end after mating. Wittenberger and Tilson (1980) suggested prolonged male–female associations should be defined as those that persist for at least 25% of the breeding season. We suggest that this criterion for pairbonding be applied to all species. From 2001 to 2003, we radio-tracked 35 (20 males, 15 females) adult Agkistrodon contortrix (L.) (Copperhead), a medium-sized North American pitviper, on a 485-ha parcel of a basalt trap-rock ridge ecosystem located 4.75 km NW of Meriden, CT. Details on topography and climate of this region are presented in Smith (2007) and Smith et al. (2009). Although 1The Copperhead Institute, PO Box 6755, Spartanburg, SC 29304. 2Department of Biology, Wofford College, 429 North Church Street, Spartanburg, SC 29303. 3Department of Biology and Center for Behavioral Neuroscience, Georgia State University, 33 Gilmer Street, SE, Unit 8, Atlanta, GA 30303-3088. 4Chiricahua Desert Museum, PO Box 376, Rodeo, NM 88056. *Corresponding author - smithcf@wofford.edu. Manuscript Editor: Rudolf G. Arndt Notes of the Northeastern Naturalist, Issue 22/1, 2015 2015 Northeastern Naturalist Notes Vol. 22, No. 1 N2 C.F. Smith and G.W Schuett Copperhead populations in more southern and western localities show 2 mating seasons per annum (Aldridge and Duvall 2002, Fitch 1960, Schuett 1992, Schuett et al. 1996, 1997), only 1 mating season occurs in this population (Smith et al. 2009, 2010). Throughout the active season, males showed greater activity-range sizes and greater movement distances than females. This trend was most pronounced during the single mating season in late summer and early fall (late July–September; Smith et al. 2009, 2010, 2012). In spring, there was no evidence of copulations, bisexual pairing, or courtship (Smith et al. 2009, 2010). During the July–September period, males showed a >17-fold increase in activity-range size and a 5-fold increase in movement distance compared to April and May. Females did not show similar large increases. Of the 42 copulations observed, 95.2% occurred during August and September (4.8% in July, 35.7% in August, 59.5% in September), concomitant with the expansion of activity ranges and increases in daily movements in males (Smith et al. 2009). Increased movement and activity-range size may represent a prolonged “scramble competition” among males to locate multiple female partners during the concentrated mating season (Duvall et al. 1992, 1993). Males in our study often courted 2 different females on consecutive days, with the distance between females ≥100 m. Likewise, it was common for a female to be in the presence of a new male within 1–2 days following copulation with another male. As a result, the 42 copulations we recorded represent matings between 21 males and 16 females (2 matings were between marked and unmarked individuals) (Smith et al. 2009). The frequency of multiple mates was 63% in females and 59% in males (maximum mating success for females was 4 mates and for males was 5 mates). In all cases, pairings persisted for ≤48 hours. Here, unlike most other observations we have documented (Levine et at. 2015; Smith et al. 2009, in press), we present observations of 1 pair of Copperheads that exhibited long-term association and hence, characteristics of pair-bonding based on the abovementioned criterion. Given a mating period spanning ~70 days (mid-July–September), a pair of Copperheads in our population would need to remain in close association for 14 consecutive days in a single breeding season for classification as pair-bonding; this pair met the criterion. An adult male (male 740) and an adult female (female 960) Copperhead were located via radio-telemetry and found to be in physical contact with each other on 3 September 2001 (Fig. 1). We located the pair 11 times over a period of 26 days (3–28 September 2001). At each location, the male was either in contact with the female or within 1 m of her, although we never observed courtship or copulation. On ~28 September 2001, near the end of the breeding season, the pair separated after they had moved approximately 200 m in the proceeding 26 days. Because movements by either individual were not directly observed during separation, it was unclear which individual initiated movement and hence separation of the pair. Given this association during the peak of the breeding season, we postulate that the pair association we describe is indicative of pair-bonding. Although the selective factors promoting the formation of pair-bonding in this population are unknown, we hypothesize that limited mating opportunities, particularly among smaller males, may be a factor. Under conditions where operational sex ratios are male-biased due to biennial or longer female reproductive cycles (as in the present study), strong competition for mates is expected between males (Emlen and Oring 1977). Previous research on male combat (competition) in Copperheads (Schuett 1997) and Sistrurus catenatus Rafinesque (Massasauga Rattlesnake) (Jellen et al. 2007) has shown that body size (snout–vent length [SVL], body mass) is important to win fights and secure mates. Additionally, in this population, SVL was correlated with reproductive success (number of offspring produced), with larger males N3 2015 Northeastern Naturalist Notes Vol. 22, No. 1 C.F. Smith and G.W Schuett siring more offspring (Levine et al. 2015). Therefore, smaller males are not as likely to sire offspring under conditions where they must compete with larger males for access to females. Perhaps significantly, the male presented here was smaller (67.3 cm SVL) than the average for the population (75.2 cm SVL ± 1.58 SE, n = 47; Smith et al. 2009). Females in this population were highly dispersed during the mating season (Smith et al. 2009), and multiple paternity has been documented, with evidence of more than1 sire found in 45% of litters tested (Levine et al. 2015). As a result, smaller males may realize greater reproductive success by forming short-term pair-bonds with unaccompanied females once located rather than by searching for additional females for which they may have to directly compete with larger males (Schuett 1997). Acknowledgments. We thank J. Victoria and L. Fortin, Connecticut Department of Environmental Protection Wildlife Division, for providing the necessary permits. S. Berube and H. Gruner provided numerous favors. We thank Harvey Lillywhite for discussing Figure 1. Putative pair-bonding in Agkistrodon contortrix (Copperhead). Male 740 and Female 960 were located together 11 times in succession for 26 days, from 3 to 28 September 2001. 2015 Northeastern Naturalist Notes Vol. 22, No. 1 N4 C.F. Smith and G.W Schuett pair-bonding in insular Cottonmouth. The American Wildlife Research Foundation, The University of Connecticut Department of Ecology and Evolutionary Biology Wetzel Fund, the Connecticut Department of Environmental Protection Non-game Fund, Sigma Xi, Georgia State University (Biology Department), Zoo Atlanta, and a National Science Foundation Predoctoral Fellowship (CFS) provided funding. Outside reviewers made helpful comments during manuscript review. This research was conducted under the supervision of the University of Connecticut Institutional Animal Care and Use Committee, protocol number S211 1201. Literature Cited Aldridge, R.D., and D. Duvall. 2002. Evolution of the mating season in the pitvipers of North America. Herpetological Monographs 16:1–25. Ardern, S.L., W. Ma, J.G. Ewen, D.P. Armstrong, and D.M. Lambert. 1997. Social and sexual monogamy in translocated New Zealand Robin populations detected using minisatellite DNA. The Auk 114(1):120–126. Birkhead, T.R., and A.P. Møller. 1992. Sperm Competition in Birds: Evolutionary Causes and Consequences. Academic Press, London, UK. 292 pp. Birkhead, T.R., and A.P. Møller. 1996. Monogamy and sperm competition in birds. Pp. 323–343, In J.M. Black (Ed.). Partnership in Birds: The Study of Monogamy. Oxford University Press, Oxford, UK. 420 pp. Black, J.M. 1996. Introduction: Pair bonds and partnerships. Pp. 3–20, In J.M. Black (Ed.). Partnership in Birds: The Study of Monogamy. Oxford University Press, Oxford, UK. 420 pp. Bull, C.M. 2000. Monogamy in lizards. Behavioral Processes 51:7–20. Bull, C.M., S.J.B. Cooper, and B.C. Baghurst. 1998. Social monogamy and extra-pair fertilization in an Australian lizard, Tiliqua rugosa. Behavioral Ecology and Sociobiology 44:63–72. Clark, R.W., G.W. Schuett, R.A. Repp, M. Amarello, C.F. Smith, and H-W Herrmann. 2014. Mating systems, reproductive success, and sexual selection in secretive species: A case study of the rattlesnake Crotalus atrox. PLoS ONE 9(3):1–12. Clutton-Brock, T.H. 1989. Mammalian mating systems. Proceedings of the Royal Society of London B: Biological Sciences 235:339–372. Dobson, F.S., B.M. Way, and C. Baudoin. 2010. Spatial dynamics and the evolution of social monogamy in mammals. Behavioral Ecology 21:747–752. Duvall, D., S.J. Arnold, and G.W. Schuett. 1992. Pitviper mating systems: Ecological potential, sexual selection, and microevolution. Pp. 321–336, In J.A. Campbell and E.D. Brodie, Jr. (Eds.). Biology of the Pitvipers. Selva, Tyler, TX. 567 pp. Duvall, D., G.W. Schuett, and S.J. Arnold 1993. Ecology and evolution of snake mating-systems. Pp. 165–200, In R.A. Siegel and J.T. Collins (Eds.). Snakes: Ecology and Behavior. McGraw-Hill, New York, NY. 414 pp. Emlen, S.T., and L. W. Oring. 1977. Ecology, sexual selection, and the evolution of mating systems. Science 197:215–223. Fitch, H.S. 1960. Autecology of the Copperhead. University of Kansas Museum of Natural History Publications 13:85–288. Fricke, H.W. 1986. Pair swimming and mutual partner-guarding in monogamous butterflyfish (Pisces: Chaetodontidae): A joint advertisement of territory. Ethology 73:307–333. Harrison, A. 2013. Size-assortative pairing and social monogamy in a neotropical lizard, Anolis limifrons (Squamata: Polychrotidae). Breviora 534:1–9. Jellen, B.C., D.B. Shepard, M.J. Dreslik, and C.A. Phillips. 2007. Male movement and body size affect mate acquisition in the Eastern Massasauga (Sistrurus catenatus). Journal of Herpetology 41:451–457. Lack, D. 1968. Ecological Adaptations for Breeding in Birds. Methuen and Company, London, UK. 409 pp. Levine, B.A., C.F. Smith, G.W. Schuett, M.R. Douglas, M.A. Davis, and M.E. Douglas. 2015. Bateman- Trivers in the 21st century: Sexual selection in a North American pitviper. Biological Journal of the Linnean Society 114(2):436–445. N5 2015 Northeastern Naturalist Notes Vol. 22, No. 1 C.F. Smith and G.W Schuett Lifjeld, J.T., P.O. Dunn, R.J. Robertson, and P.T. Boag. 1993. Extra-pair paternity in monogamous Tree Swallows. Animal Behaviour 45:213–229. Mathews, L.M. 2002. Territorial cooperation and social monogamy: Factors affecting intersexual behaviors in pair-living snapping shrimp. Animal Behaviour 63:767–777. O’Connor, D., and R. Shine. 2003. Lizards in “nuclear families”: A novel reptilian social system in Egernia saxatilis (Scincidae). Molecular Ecology 12:743–752. Palombit, R.A. 1994. Extra-pair copulations in a monogamous ape. Animal Behaviour 47:721–723. Persons, T.B., M.J. Feldner, and R.A. Repp. In press. Black-tailed Rattlesnake (Crotalus molossus). In G.W. Schuett, R.S. Reiserer, C.F. Smith, and M.J. Feldner (Eds.). The Rattlesnakes of Arizona. Eco Press, Rodeo, NM. Petrie, M., C. Doums, and A.P. Moller. 1998. The degree of extra-pair paternity increases with genetic variability. Proceedings of the National Academy of Science 95:9390–9395. Reichard, U. 1995. Extra-pair copulations in a monogamous Gibbon (Hylobates lar). Ethology 100:9–112. Rivas, J.A., and G.M. Burghardt. 2005. Snake mating-systems, behavior, and evolution: The revisionary implications of recent findings. Journal of Comparative Psychology 119(4):447–454. Schuett, G.W. 1992. Is long-term sperm storage an important component of the reproductive biology of temperate pitvipers? Pp. 169–184, In J.A. Campbell and E.D. Brodie, Jr. (Eds.). Biology of the Pitvipers. Selva, Tyler, Texas. 567 pp. Schuett, G.W. 1997. Body size and agonistic experience affect dominance and mating success in male Copperheads, Agkistrodon contortrix. Animal Behaviour 54:213–224. Schuett, G.W., H.J. Harlow, J.D. Rose, E.A. Van Kirk, and W.J. Murdoch. 1996. Levels of plasma corticosterone and testosterone in male Copperheads (Agkistrodon contortrix) following staged fights. Hormones and Behavior 30:60–68. Schuett, G.W., H.J. Harlow, J.D. Rose, E.A. Van Kirk, and W.J. Murdoch. 1997. Annual cycle of plasma testosterone in male Copperheads, Agkistrodon contortrix (Serpentes: Viperidae): Relationship to timing of spermatogenesis, mating, and agonistic behavior. General and Comparative Endocrinology 105:417–424. Shuster, S.M., and M.J. Wade. 2003. Mating Systems and Strategies. Princeton University Press, Princeton, NJ. 552 pp. Smith, C.F. 2007. Sexual dimorphism, and the spatial and reproductive ecology of the Copperhead snake (Agkistrodon contortrix). Ph.D. Thesis. University of Connecticut, Storrs, CT. Smith, C.F., G.W. Schuett, R.L. Earley, and K Schwenk. 2009. The spatial and reproductive ecology of the Copperhead (Agkistrodon contortrix) at the northeastern extreme of its range. Herpetological Monographs 23:45–73. Smith, C.F., G.W. Schuett, and K. Schwenk. 2010. Relationship of plasma sex-steroids to the mating season of Copperheads at the northeastern extreme of their range. Journal of Zoology 280:363–370. Smith, C.F., G.W. Schuett, and S.K. Hoss. 2012. Reproduction in female Copperhead snakes (Agkistrodon contortrix): Plasma steroid profiles during gestation and post-birth periods. Zoological Science 29(4):273–279. Smith, C.F., G.W. Schuett, and M. Amarello. In press. Male mating success in a North American pitviper: Influence of body size, testosterone, and spatial parameters. Biological Journal of the Linnean Society. Soulsbury, C.D. 2010. Genetic patterns of paternity and testis size in mammals. PLoS ONE DOI:10.1371/journal.pone.0009581 Westneat, D.F. 1990. Genetic parentage in the Indigo Bunting: A study using DNA fingerprinting. Behavioral Ecology and Sociobiology 27:67–76. Wittenberger, J.F., and R.L. Tilson. 1980. The evolution of monogamy: Hypotheses and evidence. Annual Review of Ecological Systems 11:197–232. Wharton, C. 1966. Reproduction and growth in the Cottonmouths, Agkistrodon piscivorus Lacépède, of Cedar Keys, Florida. Copeia 1966:149–161. Yamagishi, S., I.J. Nishiumi, and C. Shimoda. 1992. Extra-pair fertilization in monogamous Bullheaded Shrikes revealed by DNA fingerprinting. The Auk 109:711–721. Yezerinac, S.M., P.J. Weatherhead, and P.T. Boag. 1995. Extra-pair paternity and the opportunity for sexual selection in a socially monogamous bird (Dendroica petechia). Behavioral Ecology and Sociobiology 37:179–188.