Individuals try to survive in a spontaneous fashion. Survival involves feeding, avoiding negative environmental conditions, and predation. The last one is a frequent challenge to individual survival and many strategies to avoid it have evolved along the tree of life. Reptiles, in particular, show many defensive and anti-predation strategies including crypsis, locomotor escape, death feigning, bluffs and threats that typically include apparent increase in size, attempts to bite and explosive noises (Greene, 1994Greene, H.W. (1994). Antipredator mechanisms in reptiles. En: Gans, C. y Huey R.B., (eds.), Biology of the Reptilia (pp. 1-153). Washington, Branta Book.). Another way to avoid predation is to change activity patterns including nocturnality (e.g., many geckos), adopting an aquatic lifestyle (e.g., crocodilians, many turtles), or becoming fossorial (e.g., amphisbaenians, scolecophidian snakes). Moreover, heavily armored (e.g., cordylid lizards, tortoises), or highly venomous (e.g., Bitis, Naja) species also exist (Greene, 1994Greene, H.W. (1994). Antipredator mechanisms in reptiles. En: Gans, C. y Huey R.B., (eds.), Biology of the Reptilia (pp. 1-153). Washington, Branta Book.; Henderson and Powell, 2009Henderson, R.W. and Powell, R. (2009) Natural History of West Indian Reptiles and Amphibians. University Press of Florida. 495pp.; Vitt and Caldwell, 2014Vitt, L.J. and Caldwell, J.P. (2014). Herpetology: An Introductory Biology of Amphibians and Reptiles. Fourth Edition, Elsevier. 757pp.). Autohemorrhaging is a less common anti-predation mechanism that consists of the voluntary expulsion of blood through the cloaca or mouth (Greene, 1994Greene, H.W. (1994). Antipredator mechanisms in reptiles. En: Gans, C. y Huey R.B., (eds.), Biology of the Reptilia (pp. 1-153). Washington, Branta Book.). It is usually displayed as a last-resort mechanism when a predator is very close or by physical stress. This behavior has been previously reported in snakes and lizards (Smith et al., 1993Smith, D.D., Pflanz, D.J. and Powell, R. (1993) Observations of autohemorrhaging in Tropidophis haetianus, Rhinocheilus lecontei, Heterodon platyrhinos, and Nerodia erythrogaster. Herpetological Review, 24, 130-131.; Sherbrooke, 2000Sherbrooke, W.C. (2000). Sceloporus jarrovii (Yarrow’s spiny lizard). Ocular sinus bleeding. Herpetological Review, 31, 243.; Iiftime and Iftime, 2014Iiftime, A. and Iftime, O. (2014). Thanatosis and autohaemorrhaging in the Aesculapian Snake Zamenis longissimus (Laurenti, 1768). Herpetozoa, 26, 173-174.).
In the dwarf boas of genus Tropidophis (Tropidophiidae) this behavior is associated with physical stress as manipulation (Iverson, 1986Iverson, J.B. (1986). Notes on the natural history of the Caicos Islands Dwarf Boa, Tropidophis greenwayi. Caribbean Journal of Science, 22 (3-4), 191-198.), blows (Darlington, 1927Darlington, P.J. (1927). Autohemorrage in Tropidophis semicinctus. Bulletin of the Antivenin Institute of America, 1, 59.) or chemical products such as anesthetic substances (Stull, 1928Stull, O. (1928). A Revision of the Genus Tropidophis. Occasional Papers of the Museum of Zoology of the University of Michigan, 195, 1-49.; Campbell, 1951Campbell, D.G. (1951). Notes on snakes near Malvern. Natural History Notes of the Natural History Society of Jamaica, 51, 54-56.). It has been reported in T. canus (Rehák, 1987Rehak, I. (1987). Color change in the snake Tropidophis feicki (Reptilia: Squamata: Tropidophiidae). Vestník Ceskoslovenské Spolecnosti Zoologické, 51, 300-303.), T. curtus (Hecht et al., 1955Hecht, M.K., Walters, V. and Ramm, G. (1955). Observations on the natural history of the Bahaman Pigmy boa, Tropidophis pardalis, with notes on autohemorrage. Copeia, 1955 (3), 249-251.; Hoefer et al., 2019Hoefer, S., Mills, S. and Robinson, N.J. (2019). Autohaemorrhaging in a Bahamian pygmy boa, Tropidophis curtus barbouri. The Herpetological Bulletin, 150, 39-40.), T. feicki (Rehák, 1987Rehak, I. (1987). Color change in the snake Tropidophis feicki (Reptilia: Squamata: Tropidophiidae). Vestník Ceskoslovenské Spolecnosti Zoologické, 51, 300-303.), T. greenwayi (Iverson, 1986Iverson, J.B. (1986). Notes on the natural history of the Caicos Islands Dwarf Boa, Tropidophis greenwayi. Caribbean Journal of Science, 22 (3-4), 191-198.; Rehák, 1987Rehak, I. (1987). Color change in the snake Tropidophis feicki (Reptilia: Squamata: Tropidophiidae). Vestník Ceskoslovenské Spolecnosti Zoologické, 51, 300-303.), T. haetianus (Rehák, 1987Rehak, I. (1987). Color change in the snake Tropidophis feicki (Reptilia: Squamata: Tropidophiidae). Vestník Ceskoslovenské Spolecnosti Zoologické, 51, 300-303.; Smith et al., 1993Smith, D.D., Pflanz, D.J. and Powell, R. (1993) Observations of autohemorrhaging in Tropidophis haetianus, Rhinocheilus lecontei, Heterodon platyrhinos, and Nerodia erythrogaster. Herpetological Review, 24, 130-131.), T. jamaicensis (Underwood, 1952Underwood, G. (1952). Introduction to the study of Jamaican reptiles (part X). Serpentes. Natural History Notes of the Natural History Society of Jamaica, 53, 97-105.), T. melanurus (Stull, 1928Stull, O. (1928). A Revision of the Genus Tropidophis. Occasional Papers of the Museum of Zoology of the University of Michigan, 195, 1-49.; Mertens, 1946Mertens, R. (1946) Die Warn- und Droh-Reaktionen dar Reptilien. Abhandlungen der Seneckenbergischen Naturforschenden Gesellschaft, 471, 1-88.; Rehák, 1987Rehak, I. (1987). Color change in the snake Tropidophis feicki (Reptilia: Squamata: Tropidophiidae). Vestník Ceskoslovenské Spolecnosti Zoologické, 51, 300-303.; Iturriaga, 2014Iturriaga, M. (2014). Autohemorrhaging behavior in the Cuban Dwarf Boa Tropidophis melanurus Schlegel, 1837 (Serpentes: Tropidophiidae). Herpetology Notes, 7, 339-341.), T. pardalis (Domínguez and Moreno, 2003Domínguez, M. and Moreno, L.V. (2003). Serpientes del suelo. En: Rodríguez-Schettino, L. (Ed.), Anfibios y Reptiles de Cuba (pp. 98-109). Vaasa, Finland, UPC Print.), T. parkeri (Campbell, 1951Campbell, D.G. (1951). Notes on snakes near Malvern. Natural History Notes of the Natural History Society of Jamaica, 51, 54-56.; Thomas, 1963Thomas, R. (1963). Cayman Islands Tropidophis (Reptilia, Serpentes). Breviora, 195, 1-8.), T. paucisquamis (Carvalho, 1951Carvalho, A.L. (1951). Observacoes sobre “Tropidophis paucisquamis” (Müller, 1901). Revista Brasileira de Biologia, 11 (3), 239-248.), T. semicinctus (Darlington, 1927Darlington, P.J. (1927). Autohemorrage in Tropidophis semicinctus. Bulletin of the Antivenin Institute of America, 1, 59.), T. stejnegeri (Sánchez-Muñoz, 2008Sánchez Muñoz, A.J. (2008): Father Sanchez´s Web Site of West Indian natural History. Available at: http://www.kingsnake.com/westindian/. ), and T. xanthogaster (Torres et al., 2013Torres, J., Torres, O.J. and Marrero, R. (2013). Autohemorrage in Tropidophis xanthogaster (Serpentes: Tropidophiidae) from Guanahacabibes, Cuba. Herpetology Notes, 6, 579-581.). Here, we report for the first time autohemorrhaging in T. celiae, T. hendersoni and T. wrighti, as well as two new cases in T. melanurus. New reports are presented chronologically.
On 13 October 2014, during a herpetological survey in Boca de Canasí Flora Reserve, Mayabeque province, we observed autohemorrhage for the first time in an adult female of T. celiae. The individual was found at 10:13 h under a rock, at 3 m elev. and at a distance of approximately 1.7 km east from the Canasí river mouth (Torres et al., 2016Torres, J., Rodríguez-Cabrera, T.M., Marrero, R.R., Torres, O.J. and Gutiérrez, P.M. (2016). Comments on the Critically Endangered Canasí Trope (Tropidophis celiae, Tropidophiidae): Neonates, ex situ Maintenance, and Conservation. IRCF Reptiles & Amphibians, 23(2), 82-87.). When held by the neck to take measurements it started to bleed, although the amount of blood was small (less than a drop).
On 24 June 2016, during a survey in the surroundings of Pinares de Mayarí hotel (20°28’56.5” N; 75°48’14.6” W, WGS 84, ca. 689 m elev.), at 23.4 km southwest of Mayarí town, Holguín province, we observed four individuals of T. wrighti actively foraging (two on bushes, at 1 and 1.5 m height, and two on the ground) at night (21:00-23:00 h). At 18:29 h on 5 July 2016, we were measuring one of the specimens, which was being held by the neck, and after a few seconds it expelled a drop of blood from the mouth (Fig. 1) and the cavity between the eye and the spectacle filled with blood. A few seconds later the blood from the eye disappeared and the hemorrhage was arrested. The whole event had a duration of 20 seconds. This case of autohemorrhaging was very similar to that described for T. xanthogaster (Torres et al., 2013Torres, J., Torres, O.J. and Marrero, R. (2013). Autohemorrage in Tropidophis xanthogaster (Serpentes: Tropidophiidae) from Guanahacabibes, Cuba. Herpetology Notes, 6, 579-581.).
At 10:47 h on 7 August 2016, we observed autohemorrhaging in an adult female of T. hendersoni at Cueva de Los Panaderos (21°06’21.1” N; 76°08’17.6” W; WSG 84, ca. 20 m elev.) in Gibara town, Holguín province. The trope turned onto a ball while expelling blood from the mouth (Fig. 2) at the time it was being manipulated. As in T. celiae, the amount of blood was small.
Although this behavior has been reported for T. melanurus (Stull, 1928Stull, O. (1928). A Revision of the Genus Tropidophis. Occasional Papers of the Museum of Zoology of the University of Michigan, 195, 1-49.; Mertens, 1946Mertens, R. (1946) Die Warn- und Droh-Reaktionen dar Reptilien. Abhandlungen der Seneckenbergischen Naturforschenden Gesellschaft, 471, 1-88.; Iturriaga, 2014Iturriaga, M. (2014). Autohemorrhaging behavior in the Cuban Dwarf Boa Tropidophis melanurus Schlegel, 1837 (Serpentes: Tropidophiidae). Herpetology Notes, 7, 339-341.), here we present two new observations, both at the Cienfuegos Botanical Garden. We first observed abundant blood expulsion from the mouth of an individual at 11:53 h on 28 July 2013 (Fig. 3), and a second event at 13:22 h on 18 November 2013 with a duration of approximately 2 minutes (Fig. 4). Of note is that only in the two cases above from the Cienfuegos Botanical Garden, this behavior was documented with photographs, but it was observed dozens of times during a ca. five-year period (early 2012 - late 2016) while surveying this population of T. melanurus (TMRC pers. obs.). In all cases this behavior was performed while the snakes were being handled to take measurements. This confirms that autohemorrhaging occurs easily under physical stress, specifically when the head is involved. Immobilizing the specimens by the body did not elicit autohemorrhaging.
Autohemorrhaging behavior in Tropidophis apparently is present in all species of the genus. It occurs in species of different islands (Cuba, Bahamas, Hispaniola, etc.) and in the sister genus Trachyboa from Central and South America (Vidal and Hedges, 2009Vidal, N., and Hedges, S.B. (2009). The molecular evolutionary tree of lizard, snakes, and amphisbaenians. Comptes Rendus Biologies, 332,129-139.). The physiological basis of this phenomenon remains uncertain, but some authors consider that it occurs because of an increase in blood pressure associated with fright or fight behavioral response (Smith et al., 1993Smith, D.D., Pflanz, D.J. and Powell, R. (1993) Observations of autohemorrhaging in Tropidophis haetianus, Rhinocheilus lecontei, Heterodon platyrhinos, and Nerodia erythrogaster. Herpetological Review, 24, 130-131.). This behavior may have evolved to minimize predation by vertebrates. However, in Cuba, the center of the diversification of the genus (Hedges, 2002Hedges, S.B. (2002). Morphological variation and the definition of species in the snake genus Tropidophis (Serpentes, Tropidophiidae). Bulletin of Natural History Museum of London, 68(2), 83-90.) with 17 of the 33 described species (Díaz and Cádiz, 2020Díaz, L.M. and Cádiz, A. (2020). A new species of Tropidophis (Squamata: Tropidophiidae) and molecular phylogeny of the Cuban radiation of the genus. Novitates Caribaea, 16, 1-19.; Uetz et al., 2022Uetz, P., Freed, P., and Hošek, J. (Eds). (2022). The Reptile Database, http://www.reptile-database.org, accessed on 1 April 2022. ), there are few confirmed predators [Chilabothrus angulifer (Viña-Dávila and Armas, 1989Viña-Dávila, N. and de Armas, L.F. (1989). Depredación de Tropidophis melanurus (Serpentes: Tropidophiidae) por Epicrates angulifer (Serpentes: Boidae). Miscelánea Zoológica, 41, 2-3.), and Coccyzus merlini (Garrido, 1976Garrido, O.H. (1976). Aves y reptiles de Cayo Coco, Cuba. Miscelánea Zoológica, 3, 3-4.)], contrary to what happens in continental areas. Understanding the triggering factors and physiological mechanisms underlying autohemorrhaging behavior would increase the knowledge about the natural history and ecological interactions of these species with others, as well as the main pressures that they face in their habitats.