CAIMAN YACARE (Yacare Caiman). TRIPLETS

GERARDO VEGA; PABLO SIROSKI

HERPETOLOGICAL REVIEW

SOCIETY FOR THE STUDY OF AMPHIBIANS AND REPTILES

Lugar: California; Año: 2021 vol. 52 p. 568 - 569

0018-084X

The BroadsnoutedCaiman (Caiman latirostris) and Yacare Caiman(Caiman yacare) are the two crocodilian species that inhabitArgentina (Prado et al. 2012. Cuad. Herpetol. 26. Suppl 1:403–410). They can be easily differentiated based on species-specificmorphological features (e.g., cranial and nuchal structures).These two species are broadly sympatric throughout theirdistribution in Argentina, although the C. latirostris appears tobe allopatric across a larger area.In Argentina, ranching occurs for both caiman species,with wild, field-collected eggs placed into artificial incubatorsuntil hatching. Once hatched, caiman are raised in captivityuntil they reach 1.2 m in total length, at which point theyare harvested for their skins and meat; additionally, someindividuals are released back to the wild. Results from thesemonitoring programs have indicated that the harvest of eggsfrom both species is sustainable, with populations continuingto increase over time (Larriera et al. 2008. PublicaciónAsociación de Amigos de Doñana 18:141–180). Argentinianranching programs are recognized for their contribution to theconservation and biological knowledge base of both species(Villamarín et al. 2021. In Zucoloto et al. [eds.], ConservationGenetics of New World Crocodilians, pp. 1–30. Springer, Cham).An important part of the program involves recordingnesting details (e.g., GPS coordinates, number of eggs) andincubation and hatching data (e.g., incubation temperatures,time taken to hatch). After eggs arrive from the field, theyare measured (length and width) and placed into plasticincubation containers inside an incubator. Most eggs from thesame nest are usually of a similar size, unless they contain morethan one embryo.Although generally uncommon, multiple offspring hatchedfrom the same egg has been reported for several oviparousreptiles. Twinning is more common than triplets, with veryfew cases of triplets documented in reptiles (Krauss andHorn 2004. Reptiles Austral. 1(4):14–15). Twinning has beenreported in snakes (Marion 1980. Kansas Acad. Sci. 83:98–100),lizards (Hartdegen and Bayless 1999. Herpetol. Rev. 30:141;Mendyk 2007. Biawak 1:26–28; Leaché et al. 2013. GenomeBiol. Evol. 5:2410–2419), turtles (Tucker and Janzen 1997.Copeia 1997:166–173; Cooper 2009. Introducción a la MedicinaForense Veterinaria Comparada México: Ed. Acribia; Piovanoet al. 2011. Folia Zool. 60:159–166) and crocodilians (Webbet al. 1998. Crocodiles of Australia. New Holland Publishers,Fig. 3. Female Eurycea rathbuni cannibal from Primer’s Fissure,Texas, USA attempting to consume her second documented conspecific.On 31 January 2020, 26 eggs were collected from a wildC. yacare nest as part of the egg ranching program in BancoPayagua, Formosa, Argentina (26.7069°S, 58.3363°W). Seven ofthese eggs were of an unusual size and elongated in shape (Fig.1). The eggs were artificially incubated at 30–32°C in a moistvermiculite substrate. After 32 d, 25 hatchlings emerged from 22of the 26 eggs. Twenty eggs produced single hatchlings, whereasone egg produced triplets, and another egg produced twins.The remaining four eggs did not hatch, but one of them alsocontained three incompletely developed embryos. Hatchingsuccess (# of hatchings / # of eggs collected and incubated) forthis nest was 0.91. The eggs that contained triplets were muchlarger than those that contained single embryos, but not the eggcontaining twins. The hatchling triplets were also noticeablysmaller than single hatchlings, although measurements werenot taken.As it is a seemingly rare occurrence, limited information isavailable on the hatching of multiple offspring from single eggsin oviparous species. Unless these events occur in captivity,it will be difficult to determine how often this phenomenonoccurs in a species because it cannot easily be observed innature. As far as we can determine, this is the first record oftriplets in a crocodilian species