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Abstract. Jabon KJD, Gamalo LED, Responte MA, Abad RG, Gementiza GDC, Achondo MJMM. 2019. Density and diet of invasive alien anuran species in a disturbed landscape: A case in the University of the Philippines Mindanao, Davao City, Philippines. Biodiversitas 20: 2554-2560. The population density and diet composition of three invasive alien anuran species (IAS) (Kaloula pulchra, Hoplobatrachus rugulosus, and Rhinella marina), recorded from a disturbed landscape in the University of the Philippines Mindanao campus, were determined in this study. With the total area of 18 km2 covered, R. marina (3.89 ind/km2) showed to have the highest density followed by K. pulchra (0.83 ind/km2) then H. rugulosus (0.056 ind/km2). Furthermore, 20 samples of R. marina and 10 samples of K. pulchra were used for gut analysis in which all have stomach contents. Thirteen prey orders were identified in both species with different degrees of prey digestion. The Frequency of Occurrence (FOO) showed orders Spirobolida, Coleoptera, and Hymenoptera were constantly occurring in R. marina while only Hymenoptera for K. pulchra. On the other hand, Degree of Food Preference showed similarities with Hymenoptera as the most preferred prey in both species, especially for K. pulchra (2.8) as compared to R. marina (1.8). Accidental occurrence and occasionally preferred food items such as organic and inorganic matter were also present in both species. A notable record of a skink (Reptilia, Scincidae) as prey item was found in R. marina, indicative of its generalist and carnivorous diet and its potential impact on the native vertebrate fauna in the area. This study proposes that the occurrence of IAS with regards to their high density and variable prey preferences can be a factor disturbing biological diversity in an altered landscape.

This article presents the anuran species in urbanized areas, diet overlaps between native and invasive alien anuran species, and its implications on conservation and ecological health in urban environment. Visual encounter technique following the road as a transect was done to determine the diversity of anurans, and stomach content extraction was employed to analyze its diet composition. Results revealed a very low anuran diversity (Shannon-Weiner; 1.165), which is dominated by invasive alien anuran species. Jackknife 1 species richness estimator indicated that 77-100% of the anuran species in the area were already detected which includes three invasive; Rhinella marina (Linnaeus, 1758), Kaloula pulchra Gray, 1831, Hoplobatrachus rugulosus (Wiegmann, 1834), and two natives; Polypedates leucomystax (Gravenhorst, 1829), Limnonectes leytensis (Boettger, 1893). Additionally, assessing the diet of 33 randomly selected anuran samples revealed that Formicidae dominated their food item. Invasive anurans also showed more diverse diet composition compared to native frogs, in which diet overlaps were observed. In conclusion, the study supports the idea that urbanization decreases anuran diversity and supports the dominance of invasive anurans which compete for food with their native and endemic counterparts. Additionally, it is important to manage invasive anurans that dominates urban ecosystem which might affect the native and endemic species in the area and possibly in nearby pristine environment.

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