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Corresponding author: Vladislav Vergilov ( vladislav8807@gmail.com ) Academic editor: Günter Gollmann
© 2019 Vladislav Vergilov, Yurii V. Kornilev.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Vergilov V, Kornilev YV (2019) Injuries reflecting intra- and interspecific interactions in the Snake-eyed Skink Ablepharus kitaibelii (Bibron & Bory de Saint-Vincent, 1833) (Squamata, Scincidae) from Bulgaria. Herpetozoa 32: 171-175. https://doi.org/10.3897/herpetozoa.32.e37735
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The Snake-eyed Skink’s intra- and inter-specific interactions and their impacts on the individual (e.g. injuries) have received little attention so far. As part of copulation, male lizards bite the females; observations confirm an old report that bites occur in the fore side of the body, along with more recently published information about the back side. Additionally, out of 435 individuals observed in situ, 10 had missing extremities (toes, ankles, etc.); however, further studies should identify the causes of such injury, e.g. male-male combat, predators. For the first time, an adult male was observed biting a juvenile ex situ; the specific reasons, however, remain unknown. This report should generate further interest in ecological and behavioral studies, assessing the costs and benefits to potential territorial defense, intra-specific combat, and predator pressure and escape mechanisms.
aggression, biting, copulation, limb, lizard, tail
The Snake-eyed Skink Ablepharus kitaibelii (Bibron & Bory de Saint-Vincent, 1833) is a small scincid lizard, with a total length of up to 12 cm for males and 12.8 cm for females in Bulgaria (
While it is a generally understudied species, several key studies outside Bulgaria have focused on its distribution and taxonomy (e. g.
However, scarce information has been published about its intra- and inter-specific physical interactions and their impacts on individuals. According to
Reports of injuries (e.g. caused by predators) or their causes are scarce.
А second tail may also regrow after impartial autotomy or erroneous regrowth following a complete autotomy, resulting from an aggressive encounter (
Following a rare observation of an intra-specific antagonistic behavior, we compiled additional unpublished observations from Bulgaria to provide the first brief overview of physical injuries resulting from intra- and inter-specific interactions in the Snake-eyed Skink.
We reviewed data obtained from several sources, including in situ and ex situ observations.
We recorded body injuries in wild-caught individuals, relying on two sources. Between 2013 and 2016, VV carried out an intensive capture-mark-recapture (CMR) study on a population of A. kitaibelii from Pastrina Hill, near the town of Montana in north-western Bulgaria (located at cell FP80 from the 10×10 km MGRS/UTM grid; datum: WGS84, GCS). Upon capture, each individual was marked, measured, photographed, and released on the spot (further details presented in
Furthermore, we made an observation of intra-specific aggression during a laboratory experiment on locomotion performance of A. kitaibelii (Vergilov et al., in prep.). In September 2018, we tested thirteen adults and seven juveniles from Bezden Village (UTM cell FN75). All individuals were initially placed in a terrarium (dimensions: 50L×30W×30H cm) with ~3 cm of coconut fiber substrate and oak leaves as hiding place. Within the next 3–4 days individuals that had been filmed were progressively transferred to smaller boxes (dimensions: 18L×18W×8H cm) housing only 2–3 individuals and covered with the same substrate. Animals were kept at ~22 °C; due to the nature of filming, no regular photoperiod could be maintained. Individuals were provided ample small Tenebrio molitor L. larvae and water ad libitum. In a separate enclosure, single lizards were gently stimulated to move for testing their locomotion performance, while being exposed for 30–40 min to a high-intensity light, necessary for the high-speed filming of the trials.
We present the types of injuries based on their severity and probable frequency of occurrence in nature.
Expectedly, bite marks on female individuals as a result of copulation were observed during the reproductive season (April–May) throughout the country – four individuals from Gabrovitsa, Ihtimanska Sredna Gora Mnt. (UTM cell GM48; pers. comm. E. Vacheva); one from near Ogosta Dam, Montana Town (FP70); and several individuals from Pastrina Hill, near Montana Town.
Males had bitten the females not only on the hind side of the body, but on the fore side as well (two females from Gabrovitsa: Fig.
Although likely to occur in nature as a result of male-male combat, we have not recorded bite marks on male individuals.
Overall, out of the 415 marked individuals during the CMR study, 2.17% (n = 9; 3 males, 5 females, 1 juvenile) had missing limbs or toes. When initially captured, only two (an adult female and a juvenile) were detected missing the “ankle” of the left hind limb. In the remaining cases, the injuries were obtained between the capture and a subsequent recapture (average: 386 days, range: 67–742). All such injuries of recaptured individuals were of adults: two females were missing a part of the left hind limb (Fig.
In addition, among the 20 lizards captured at Bezden, one adult male (described again in the next section) had missing phalanges of the left hind limb and was missing part of the middle finger of the right hind limb (Fig.
During the locomotion experiment, we housed two adults and one juvenile in a smaller container. Approximately two days later, we made a chance observation of an intra-specific aggression. An adult male (Snout-Vent Length, SVL: 4.2 cm, Tail Length, TL: 3.2 cm, regrown; Weight, W: 0.83 g) was biting the juvenile (SVL: 3.0 cm, TL: 3.95 cm, W: 0.29 g) on the head and shaking it (Fig.
The Snake-eyed Skink is a small lizard with a secretive life. This makes studying the behavior and intra- and interspecific interactions very difficult. Studies, mostly from 19th to mid-20th century, provide sparse data and observations on behavior (
Although there are several publications concerning egg deposition in A. kitaibelii (
Traumas leading to missing extremities are likely caused by either of two sources: intra-specific aggression and depredation. Although
A second source of such traumas are depredation attempts, during which either the predator bit off a piece or the lizard twisted its body violently in an attempt to escape, leading to a loss of an extremity. Such escape behaviors have been reported (
Territorial defense might expose individuals to high predator pressure, and injuries sustained in intra-specific combat could have a high cost on fitness. Future studies should evaluate the costs and benefits of such behaviors for A. kitaibelii, the extent of their occurrence in nature, and the impacts of predators.
Regarding the intra-specific interaction we observed, we can only stipulate potential causes. A specific stressful situation leading to this behavior is unlikely; instead it might be a result of repetitive stress. Still, overall, animals did not seem to be abnormally stressed. Although some animals exhibited rapid escape movements (indicative of stress) especially at the beginning of the locomotion experiment, generally they seemed to habituate rapidly, evidenced by their propensity to predominantly utilize slow to very slow escape movements. Individuals also readily fed in between filming attempts, both indicative of habituation and decreasing the probability that the aggression was caused by hunger. Furthermore, we have not found reports on cannibalism. Although individuals can bite as a defensive behavior (
We are grateful to Emiliya Vacheva for the personal information and pictures of female lizards with bitemarks, to Boyan Zlatkov for the advice and technical support, to Karin Ernst for help with a German publication, and to Kostadin Andonov for help with a Hungarian publication. We thank Dušan Jelić and an anonymous reviewer who improved the manuscript. This research was partially funded by project № M11/12 of the National Scientific Research Fund and carried under permits for scientific purposes No. 411/14.07.2011, No. 520/23.04.2013 and No. 656/08.12.2015 from the Ministry of Environmental and Water, Bulgaria. The authors declare no competing interests.