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Universidad de la
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Momentos de Ciencia 8:(2), 2011
CIENCIA
Amputation of digits in males of the yellow-headed gecko Gonatodes albogularis Mauricio Peñuela Grupo de Estudio y Trabajo en Genética (GETEG). Facultad de Ciencias, Universidad del Valle, Cali, Colombia. Recibido 15 de Diciembre de 2010; aceptado 27 de Abril de 2011 Abstract Several types of aggressive behaviors have been reported in gekkonid lizards, in some species both males and females exhibit this type of behavior. The majority of aggressive behavior is non-invasive, however, in some occasions bites can occur and may cause injury. This study reports the presence of fingers or phalanges cut in some adult males of Gonatodes albogularis, and relates it to evidence of aggressive behavior between males. None of the females examined in this study presented amputations of digits. Aggressive behaviour related to territoriality and other factors are discussed as possible causes of amputations in males of this species of lizard. Key Words: Digit loss, phalanges, aggressive behavior, tree lizard. Resumen Numerosos tipos de comportamientos agresivos han sido reportados en gecónidos, en algunas especies tanto machos como hembras exhiben este tipo de comportamiento. La mayoría de los comportamientos agresivos son no invasivos, sin embargo, en algunas ocasiones mordeduras pueden causar lesiones. Este estudio reporta la presencia de dígitos o falanges amputados en algunos machos de Gonatodes albogularis, y lo relaciona como evidencia del comportamiento agresivo entre machos. Ninguna de las hembras examinadas en el presente estudio exhibe amputación de dígitos. El comportamiento agresivo relacionado con la territorialidad y otros factores, se discuten como posibles causas de las amputaciones en los machos de esta especie de lagarto. Palabras clave: Perdida de dígitos, falanges, comportamiento agresivo, lagarto arbóreo..
Introduction
often observed on tree trunks, branches, and wooden objects, sometimes hanging upside down (Carr, 1939; Fitch, 1973; Schwartz & Henderson, 1991; Köhler, 2003). Males are especially easily detectable because of their bright yellow heads. Sexual maturity can be reached at six months of age (Fitch, 1973), and intraspecific communal nesting has been reported (Sexton & Turner, 1971; Fitch, 1973). Females oviposit single eggs several times each year (Köhler, 2003) and eggs may take 2–4 months to hatch (Fitch, 1973; Köhler, 1999, 2003). Reproduction may occur year-round (Fitch 1973), but reduced activity and reproduction occur during the December–May dry season (Sexton & Turner, 1971; Telford, 1971; Fitch, 1973) (see Krysko, 2005). Adult males are known to defend a specific area and exhibit tail-waving as a territorial signal (Fitch, 1973), a pursuit-deterrent signal to potential predators and may also have a social function (Bohórquez et al., 2010). Aggressive behavior has been reported in gekkonid lizards. Positions such as approach, retreat, tail wave, chase, lateral advance, throat
The yellow-headed gecko, Gonatodes albogularis (Duméril and Bibron,1836), is native to the lowlands of Chiapas, Mexico, on the Pacific slope and Guatemala on the Atlantic slope, Colombia and western Venezuela (Savage, 2002), and in Aruba, Curaçao, Tortuga, Orchila, Gorgona; Hispaniola, Jamaica, Cayman Islands, and Cuba (Barbour, 1910; Barbour & Ramsden, 1919; Schwartz and Henderson, 1991). This species was introduced on Key West in the lower Florida Keys, United States (Carr, 1939, 1940; King & Krakauer, 1966; Wilson & Porras, 1983; Schwartz & Henderson, 1991; Meshaka et al., 2004), as well as on Grand Cayman, Cayman Islands (Williams, 1964; Schwartz & Thomas, 1975) where it has since disappeared (Seidel & Franz, 1994). (see Krysko, 2005). G. albogularis is a conspicuous diurnal lizard that is found on trees, in holes and crevices, and under debris (Carr, 1939; Fitch, 1973; Schwartz & Henderson, 1991; Köhler 2003). This species is
Autor para correspondecia: E-mail: mauricio.penuela@hotmail.com
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Results
inflation and bites have been quantified (Demeter & Marcellini, 1981), but no study reported the loss of digits due to aggressive behavior. Ellingson (1994) describes that In G. albogularis males are frequently in aggressive contests with other males. During preliminary field observations, we noted that some males of G. albogularis presented digits cut while no female presented this condition. Would be possible that the digit loss in this species was a common pattern? Could this condition be associated with gender or size of individuals? Is possible that aggressive behavior may result in digit loss? This study examined whether the loss of digits may be a sign of aggresive behavior for this species, how gender and a size may be related with those facts, and discuss other possible explanations.
A total of 66 individuals of G. albogularis from the collection coming from different parts of Colombia were examined. We found that 36,66% of adult males and 33,33% of juvenile males presented digit amputations, while no female pre sent ed th is co nditi on , a nd neith er did indeterminated juveniles, (Table 1). Eleven of thirty adult males and one of three juvenile males showed some phalanges cut (Table 2). There were six cases of fingers cut in the front legs and 14 in the hind legs. At the end of the cohabitation experiment, two males showed amputated digits and no female with this condition. For the first male, 2D of front right foot and 3D and 4D of right hind foot were amputated, while the second male was missing the 4D from the left hind foot. This result shows that aggressive behavior between males can be a cause of the phalanges cut.
Materials and methods
Table 1. Number of specimens analyzed, number of specimens with amputated digits and percentage of female and male amputees, for both adults and juveniles of Gonatodes albogularis from Colombia.
All 66 speciems of G. albogularis of the Colección de vertebrados anfibios y reptiles (UV-C) from the Universidad del Valle were examined for this study. The specimens were cataloged by gender (sexual dimorphism in coloration) and juvenil or adult state. Adult state was determined in individuals having 30 mm higher snout-ventral length (SVL). The digit order (D) was considered medial to lateral, in which the most medial was the “first” digit. From the museum specimens analysed we noted the number of individuals of each age class and sex having any phalange cut, and calculated the corresponding percentages. Additionally, we annotated how many phalanges were cut in each of the fore and hind feet. A cohabitation experiment was done, with the objective to determine if any aggressive behavior can affect the digits integrity of individuals and if the gender was involved. Five adult males and five adult females without any phalange cut were captured from the Microestación Biológica Experimental of the Universidad del Valle. They were maintained in a plastic container of 21cmx 21cmx 45cm for two months. Artifitial habitat consisted of a small trunk and a pierced br ic k. Foo d w a s a dmin is tre d w e ek ly a n d consisted of different types of insects like flies, little cockroaches, ants and small crickets. Water was always available. After the experiment all individuals were released to their natural habitat.
specimens Specimens Percentage with digits of amputees amputated Adult females Juvenile females Total of females Adult males
23
0
0
8
0
0
31
0
0
30
11
36,66
Juvenile males Total of males Undetermin ed juveniles
3
1
33,33
33
12
36,36
2
0
0
Discussion Demeter and Marcellini (1981) established a behavorial repertory for Gonatodes vittatus, gave a qualitative description of courtship and aggression, and analyzed some aspects of its social behavior wiht regard to interand intrasexual an dominance/ subordinance interactions. They report posistions such as approach, retreat, tail wave, chase, lateral advance, throat inflation and bites. Similar behavior have been reported to
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Table 2. Male specimens with amputated digits, total of feet affected and total of digits amputated per individual. (* represent juvenile male). Front Specimens
Hind
left right left foot foot foot
1D, 2D, 3D 4D
UV 250 UV-C 0644 UV-C 14059
1D
2D
UV-C14060 UV-C15216*
right foot
4D
1D
1D 2D
UV-C 2435 UV-C 4364
3D 1D 3D, 4D 3D
UV-C 5004 UV-C 5006 UV-C 5011
1D
UV-C 5014 UV-C 5017
Total of feet Total of with digits digits amputated amputated 1
3
1
1
4
4
1
1
1
1
1
1
1
1
1
2
1
1
1
1
4D, 5D
1
2
3D
2
2
3D
would frequently break off the encounter and attempt to escape. In G. albogularis male chases accompanied by bites, could explain why most of the males tested in this study had digit amputees on their hind legs. Furthermore amputation of neighboring digits of hind legs was evident. G. albogularis males suffer more predatory attacks than females (Ellingson, 1194). Natural predators or simple accidents can explain the digit loss too, but these factors can not explain why any female present digit cut. The absence of digit lost in females could indicate that these are not victims of any kind of invasive attacks. It can indicate that G. albogularis females play a passive role in social behavior, different from females of G. vittatus, which display a very aggresive behavior similar to males (Demeter & Marcellini, 1981). Bites and straddle in female have been reported as an aggressive behavior by Stamps (1977). A high degree of female aggression and behavioral similarity between the sexes is also found in other diurnal geckos (Kastle, 1964; Greer, 1967). On the other hand, the females of nocturnal geckos show lower aggression and a behavioral suppression similar to that described for female iguanid liz a rds (Marce l lin i , 1 977). Ho we ve r , if G . albogularis females display aggresive conduct, this could not be reflected in the amputation of
others gekkonid lizards (Greenberg, 1943; Kastle, 1964; Bustard, 1965; Greer, 1967; Marcellini, 1977; Langebaek, 1979). Ellingson (1994) describes that In G. albogularis males with a yellowish head win mor frequently in aggressive contests with other males and are prefferred by females over those with an orange head. Postures such as approach, retreat, tail wave, chase, lateral advance and throat inflating are not invasive conducts and can be very useful in territorial dispute, because they avoid physical contact and possible injury. However in some cases these demonstrations of superiority in males can result in biting attacks. Amputation of digits could be one of the main consequences of this invasive behavior. Digit loss was an underestimate factor of aggressive behavior in gekkonid lizards. This study is the first to suggest that digit loss could be the consequence of aggressive behavior in the gekkonid lizard G. albogularis. The evidence of this behavior is only seen in male individuals. This fact affects a large percentage of the male population, as it is common to find digitamputees in wild specimens. Territoriality is the main cause of conflict between males, Demeter and Marcellini (1981) describe that males of G. vittatus after exhibiting no invasive behaviors,
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