American bullfrog (Lithobates catesbeianus) distribution, impact on native amphibians and management priorities in San Carlos, Uruguay

Biological invasions are a major cause of biodiversity and ecosystem services loss. However, information on distribution and impacts is limited for many alien species, restricting the development of local management measures. The aim of this study is: to identify the current situation of the American bullfrog (Lithobates catesbeianus) invasion focus in San Carlos (Maldonado, Uruguay); to evaluate its impacts on native anurans; and to provide management tools. Between 2017 and 2019, 75 permanent ponds were sampled, finding an expanding bullfrog population (occupying 32 ponds, in 16.5 km 2 ). Results show that native anuran richness was lower in the invaded ponds. Observed impacts were greater for the aquatic frog Pseudis minuta, probably due to greater encounter rates with the invader. The abundance of tadpoles was also lower in the invaded ponds. The local pond network was explored using graph theory, evaluating its topological role and centrality. In this network, a list of priority ponds was generated to prevent local bullfrog expansion. Given the relatively small size of this population, eradication seems feasible. Focusing on the key nodes could prevent further expansion, by using spatial prioritization to organize the recommended management of the pond network.Agencia Nacional de Investigación e Innovació

First report of satellite males during breeding in <i>Leptodactylus latrans</i> (Amphibia, Anura)

A male Leptodactylus latrans was observed calling within a foam nest located at about 40 cm from the edge of the pond. The male was collected (voucher deposited at the Herpetological Collection of the Museo Nacional de Historia Natural, Montevideo, Uruguay, MNHN 9476). Ten minutes after the calling male was removed, we observed an amplectic L. latrans pair laying eggs in the same nest. In addition, a third male was at the edge of the foam nest and sporadically swam under the amplectic pair.Asociación Herpetológica Argentina (AHA

First report of satellite males during breeding in <i>Leptodactylus latrans</i> (Amphibia, Anura)

A male Leptodactylus latrans was observed calling within a foam nest located at about 40 cm from the edge of the pond. The male was collected (voucher deposited at the Herpetological Collection of the Museo Nacional de Historia Natural, Montevideo, Uruguay, MNHN 9476). Ten minutes after the calling male was removed, we observed an amplectic L. latrans pair laying eggs in the same nest. In addition, a third male was at the edge of the foam nest and sporadically swam under the amplectic pair.Asociación Herpetológica Argentina (AHA

Graph theory as model to understand American bullfrog invasion in Uruguay

In this work it is presented a graph theory approach for the characterization of the data-set of ponds invaded by the aquatic amphibian Lithobates catesbeianus in the period 2007-2022 in Acegu´a (Uruguay). The topological characterization of the network of ponds with a mobility threshold distance of 700 m is presented. The vulnerability analysis of ponds is carried out using centrality metrics, community analysis and evaluating the connection probabilities between nodes, the goal is to classify nodes to prioritize the invasion control.Agencia Nacional de Investigación e Innovació

Skin-mates or neighbors? A seasonal study of amphibian chytrid and dermocystid infection in <i>Boana pulchella</i> (Anura: Hylidae)

We studied in this work the prevalence of two eukaryotic skin pathogens in a population of the frog Boana pulchella (Anura, Hylidae) from southeastern Uruguay, the fungus Batrachochytrium dendrobatidis (Rhizophydiales) and the protoctistan Valentines rwandae (Ichthyosporea, Dermocystida), between 2012 and 2014. In both cases higher prevalences were recorded in cooler seasons, winter and early spring for B. dendrobatidis (0.78 and 0.95 respectively) and autumn for V. rwandae (0.33 and 0.49), with mean temperatures between 11.5 and 17.8°C. No cases of infection were detected in summer. In both cases the probability of infection was strongly influenced by season (and also the year for B. dendrobatidis), but in neither case the occurrence of the other pathogen was significant. The parasitic cycles seem to occur independently and are likely strongly associated to environmental temperatures. Future field studies on amphibian eukaryotic pathogens from temperate areas of South America should consider seasonal variations.En este trabajo se estudió la prevalencia de dos patógenos cutáneos eucariotas en una población de la rana Boana pulchella (Anura, Hylidae) del sureste de Uruguay, el hongo Batrachochytrium dendrobatidis (Rhizophydiales), y el protista Valentines rwandae (Ichthyosporea, Dermocystida), entre 2012 y 2014. En ambos casos las prevalencias más altas se registraron en épocas frías, invierno y primavera temprana para B. dendrobatidis (0,78 y 0,95 respectivamente) y otoño para V. rwandae (0,33 y 0,49), con temperaturas medias entre 11,5 y 17,8°C. No se detectaron casos de infección en verano. La probabilidad de infección en los dos casos está fuertemente influenciada por la estación (y además por el año para B. dendrobatidis), pero no por la ocurrencia del otro patógeno. Ambos ciclos parasitarios parecen ocurrir independientemente, y son probablemente condicionados en gran medida de la temperatura ambiental. Futuros estudios de campo sobre patógenos eucariotas en anfibios de zonas templadas de Sudamérica deberán tener en cuenta variaciones debidas a la época del año.Asociación Herpetológica Argentin

Assessment of the calling detection probability throughout the day of two invasive populations of bullfrog (Lithobates catesbeianus) in Uruguay

Bullfrog invasion is a major conservation concern in South America, so there is an urgent need to detect and monitor its many invasion foci. Amphibian sampling methods commonly use calling display, specifically the nuptial calls of males. With the aim of obtaining the better day period to sample and monitor Lithobates catesbeianus presence, we recorded its calls at three ponds in two invaded localities in Uruguay (Aceguá, Cerro Largo, and San Carlos, Maldonado) during the reproductive season. Then, we studied the records, obtaining a subsample of calling intensity at the first 5 minutes for each hour. We detected that vocalization intensity remained almost constant between 20:00 and 05:00 h. Detection probability remained high and constant during this period, and then decreased. Therefore, bullfrog displays a constant calling activity during the nights of its reproductive period, even longer than native anurans. This long calling period facilitates its detection during nocturnal sampling

First Report of Satellite Males during Breeding in \u3cem\u3eLeptodactylus latrans\u3c/em\u3e (Amphibia, Anura)

Individual males can adopt alternative mating tactics. The occurrence of satellite males is a common behaviour across anuran taxa (e.g., Lithobates clamitans, Wells, 1977; Anaxyrus cognatus, Krupa, 1989; Dendropsophus ebraccatus, Miyamoto and Cane, 1980; Rhinella crucifer, Forester and Lynken, 1986). Satellite males take peripheral positions to calling males, and adopt alternate mating tactics in an attempt to intercept females that are attracted to calling males (Wells, 2007) to increase their own mating success. Satellite males could have an inexpensive form of mate-locating, avoiding predators, and saving energy (Arak, 1983). Furthermore, this strategy could play an important role in the genetic structure of populations (Lodé and Lesbarrères, 2004)

Skin-mates or neighbors? A seasonal study of amphibian chytrid and dermocystid infection in <i>Boana pulchella</i> (Anura: Hylidae)

We studied in this work the prevalence of two eukaryotic skin pathogens in a population of the frog Boana pulchella (Anura, Hylidae) from southeastern Uruguay, the fungus Batrachochytrium dendrobatidis (Rhizophydiales) and the protoctistan Valentines rwandae (Ichthyosporea, Dermocystida), between 2012 and 2014. In both cases higher prevalences were recorded in cooler seasons, winter and early spring for B. dendrobatidis (0.78 and 0.95 respectively) and autumn for V. rwandae (0.33 and 0.49), with mean temperatures between 11.5 and 17.8°C. No cases of infection were detected in summer. In both cases the probability of infection was strongly influenced by season (and also the year for B. dendrobatidis), but in neither case the occurrence of the other pathogen was significant. The parasitic cycles seem to occur independently and are likely strongly associated to environmental temperatures. Future field studies on amphibian eukaryotic pathogens from temperate areas of South America should consider seasonal variations.En este trabajo se estudió la prevalencia de dos patógenos cutáneos eucariotas en una población de la rana Boana pulchella (Anura, Hylidae) del sureste de Uruguay, el hongo Batrachochytrium dendrobatidis (Rhizophydiales), y el protista Valentines rwandae (Ichthyosporea, Dermocystida), entre 2012 y 2014. En ambos casos las prevalencias más altas se registraron en épocas frías, invierno y primavera temprana para B. dendrobatidis (0,78 y 0,95 respectivamente) y otoño para V. rwandae (0,33 y 0,49), con temperaturas medias entre 11,5 y 17,8°C. No se detectaron casos de infección en verano. La probabilidad de infección en los dos casos está fuertemente influenciada por la estación (y además por el año para B. dendrobatidis), pero no por la ocurrencia del otro patógeno. Ambos ciclos parasitarios parecen ocurrir independientemente, y son probablemente condicionados en gran medida de la temperatura ambiental. Futuros estudios de campo sobre patógenos eucariotas en anfibios de zonas templadas de Sudamérica deberán tener en cuenta variaciones debidas a la época del año.Asociación Herpetológica Argentin