Analysis of Diet Composition and Morphological Characters of The
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Official journal website: Amphibian & Reptile Conservation amphibian-reptile-conservation.org 13(1) [General Section]: 111–121 (e172). Analysis of diet composition and morphological characters of the little-known Peruvian bush anole Polychrus peruvianus (Noble, 1924) in a northern Peruvian dry forest 1Antonia Beuttner and 2,*Claudia Koch 1Universität Tübingen, Geschwister-Scholl-Platz, 72074 Tübingen, GERMANY 2Zoologisches Forschungsmuseum Alexander Koenig (ZFMK), Adenauerallee 160, 53113 Bonn, GERMANY Abstract.—Analyses of diet composition are an important element of studies focusing on biological diversity, ecology, and behavior of animals. Polychrus peruvianus was found to be a quite abundant lizard species in the northern Peruvian dry forest. However, our knowledge of the ecology of this species remains limited. Herein, we analyze the species dietary composition and the morphological features that may be related to the feeding behavior. Our results show that P. peruvianus is a semi-herbivorous food generalist, which also consumes faunistic prey. All age groups prefer mobile prey as sit-and-wait predators. However, during ontogenesis, plant material becomes the main component in the diet of adult specimens. Keywords. Iguania, bite force, ontogenetic change, foraging strategy, stomach contents, food niche, feeding behavior, Marañón river Citation: Beuttner A, Koch C. 2019. Analysis of diet composition and morphological characters of the little-known Peruvian bush anole Polychrus peruvianus (Noble, 1924) in a northern Peruvian dry forest. Amphibian & Reptile Conservation 13(1) [General Section]: 111–121 (e172). Copyright: © 2019 Beuttner and Koch. This is an open access article distributed under the terms of the Creative Commons Attribution License [At- tribution 4.0 International (CC BY 4.0): https://creativecommons.org/licenses/by/4.0/], which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The official and authorized publication credit sources, which will be duly enforced, are as follows: official journal title Amphibian & Reptile Conservation; official journal website: amphibian-reptile-conservation.org. Received: 07 December 2017; Accepted: 26 July 2018; Published: 14 March 2019 Introduction and Caldwell 2013). In contrast active foraging species normally prey on sedentary (e.g., insect larvae), clustered The study of diet and trophic relationships between a (e.g., termites), or hidden prey (e.g., scorpions) (Bergallo species and its environment is a central theme in ecology. and Rocha 1994; Huey and Pianka 1981; Magnusson et Field and museum-based studies provide insights about al. 1985; Nagy et al. 1984; Vitt and Caldwell 2013). Es- feeding behavior, foraging strategies, and sexual or onto- pecially based on morphological variation, there may ex- genetic variation within species (Futuyama 1998; Clark ist differences in size or type of preferred prey between 2002). According to their type of prey, lizards can be di- males and females (species with a distinct sexual size di- vided into different trophic categories: insectivorous, her- morphism) or between adults and juveniles (Pough 1973; bivorous, carnivorous, or omnivorous (Vitt and Pianka Verrastro and Ely 2015; Vitt and Caldwell 2013). It is 2007). Some lizard species even show an ontogenetic generally accepted that lizards with higher and broader shift in diet from carnivory to omnivory, or even to her- heads are capable of producing stronger bite forces bivory (Cooper and Vitt 2002; van Leeuwen et al. 2011). (Campos 2016; McBrayer and Corbin 2007; Miles et al. They can be food generalists that ingest a random sample 2007) and are thus able to consume harder dietary items of prey available (and also plant material), or specialists (Herrel et al. 2001a, b; Herrel 2007; Huyghe et al. 2009; that select specific food items (Vitt and Caldwell 2013). Verwaijen et al. 2002). Campos (2016) and Herrel et al. Depending on a species’ behavior to locate and capture (2006) subdivided food items in “hard,” “intermediate,” prey, two basic foraging strategies are recognized: “sit- and “soft” prey, the latter requiring the lowest bite forces. and-wait” and active foraging (Vitt and Caldwell 2013). Knowledge of a species` diet as part of its natural history “Sit-and-wait” foragers remain motionless and wait for may be crucial for the implementation of conservation mobile prey (e.g., spiders, beetles, dipterans, and but- actions for a species and its environment (Greene 1994; terflies) to pass through their field of vision (Anderson Verrastro and Eli 2015). and Karasov 1988; Bergallo and Rocha 1994; Huey and Until a few years ago the polychrotid lizard Poly- Pianka 1981; Magnusson et al. 1985; Nagy et al. 1984; chrus peruvianus (Squamata: Iguania) was only known Pianka 1970; Pianka and Parker 1975; Toft 1985; Vitt from a few specimens, and sufficient data was lacking Correspondence. * [email protected] Amphib. Reptile Conserv. 111 March 2019 | Volume 13 | Number 1 | e172 Beuttner and Koch for a proper assessment of its conservation status. Conse- Material and Methods quently, it was listed as Data Deficient by the IUCN Red List of Threatened Species (Cisneros-Heredia 2010). In the framework of an intensive herpetological inven- Recent fieldwork (Koch et al. 2011) provided new in- tory in the inter-Andean dry forest valleys of the Mara- sights into the distribution and ecology of the species and ñón river and its tributaries we collected a total number contributed to an updated assessment of its conservation of 64 individuals of Polychrus peruvianus (Koch et al. status. Hence, the species is now listed as Vulnerable by 2018). Most of these specimens were deposited in the the IUCN due to its relatively small extent of occurrence collections of the Centro de Ornitología y Biodiversidad (~12.000 km²), the low number of known locations (<5), (CORBIDI), in Lima, Perú, and the Museo de Histo- and a decline in the extent and quality of its habitat, due ria Natural de la Universidad Nacional de San Agustín to logging, agricultural expansion, and hydroelectric dam (MUSA), in Arequipa, Perú. However, we were allowed constructions (Venegas et al. 2017). Nevertheless, dur- to export 24 individuals (9 males, 10 females, 5 juveniles) ing our intensive fieldwork in different inter-Andean dry for further examination and to add them to the collection forest regions in northern Peru, we could lately provide of the Zoologisches Forschungsmuseum Alexander Koe- records of P. peruvianus for 12 of 28 surveyed localities nig (ZFMK), in Bonn, Germany. The specimens housed in the departments of Amazonas and Cajamarca. As per in the ZFMK built the basis of the dietary analysis, pre- the research permits, we collected up to six specimens sented herein. We detected these specimens between per locality for preservation and examination, to further May 2008 and December 2009 at different localities dur- contribute to the knowledge of this scarcely known spe- ing visual encounter surveys after nightfall, when they cies. Surprisingly, the species seemed to be quite abun- were sleeping on branches of trees and shrubs in heights dant in most surveyed regions, as we often found many between 1.5 m and 7.0 m above the ground (Koch et al. more individuals than just the ones we were allowed to 2018). We collected one individual in May 2008 (ZFMK collect (Koch et al. 2011, 2018). The species is further 88707), two in June 2008 (ZFMK 88708-09), four in July known from the Zamora-Chinchipe province in south- 2008 (ZFMK 88710-13), four in March 2009 (ZFMK ern Ecuador and Peruvian department of Piura at eleva- 90817-20), two in April 2009 (ZFMK 90821-22), and tions of 400−1,750 m a.s.l. (Carrillo and Icochea 1995; eleven in December 2009 (ZFMK 90823-33). Exact lo- Duellman 1979; Gorman et al. 1969; Koch et al. 2011; calities of each specimen are given in the Appendix. We Noble 1924; Peters and Donoso-Barros 1970; Schlüter either captured the specimens by hand or by use of a fish- 2010; Torres-Carvajal et al. 2017; Yañez-Muñoz et al. ing net and euthanized them by an injection of the veteri- 2006). Polychrus peruvianus is diurnal and highly arbo- nary anesthetic T61 the following morning, no later than real, being almost exclusively found on trees or shrubs 10 hours after their capture, to guarantee that the stomach (Koch et al. 2011). Males and females show a conspicu- contents were little digested and in good condition for ous sexual dimorphism in coloration; females have lime identification. After fixation in 10% formalin for 24 to green heads and a straight white stripe laterally between 48 hours, the specimens were preserved in 70% ethanol. the axilla and the insertion of the hind limbs, whereas the Sexes of the specimens were determined by coloration heads of males are brownish and a white lateral stripe is and/or by internal reproductive organs (testicles or ova- lacking (Koch et al. 2011). The congeners P. marmora- ries) or by the presence of everted hemipenes. We catego- tus and P. acutirostris are known to feed on arthropods rized individuals with a snout-vent-length (SVL) of less as well as plant material (Garda et al. 2012; Koski et al. than 100 mm as juveniles, since none of the dissected liz- 2016). However, the only available information regard- ards up to this size had mature gonads. ing the diet of P. peruvianus derives from a single indi- Definition of head length, head width, and head height vidual from Tingo in the Peruvian department of Amazo- follows Meyers et al. (2002). Measurements of head nas, whose stomach contained several hymenoptera and (length, width, height), body (SVL, width) and tail length a leaf fragment (Gorman et al. 1969). of the lizards and dimensions of prey items (length, width) In the present study, we sought to describe the diet were taken with a dial caliper (0 – 150 mm; to the nearest of populations of Polychrus peruvianus from the inter- 0.01 mm) and weights of bodies, fat bodies, and stomachs Andean dry forest valley in northern Peru to provide were calculated with a digital weighing machine (Alma- information that may be relevant for the establishment sa® MT 7; max.