Italian agile frog

Species of amphibian

The Italian agile frog (Rana latastei), also known as Lataste's frog, is a species of frog in the family Ranidae (true frogs). The species is native to southern Europe, primarily found in the Po River Basin of Italy. It is one of the most endangered amphibian species in Europe, with its populations declining sharply in recent years, and has been the focus of multiple conservation plans.

The specific name, latastei, is in honor of French herpetologist Fernand Lataste.

Rana latastei may attain a head body length of Females tend to be slightly larger than males. Most frogs have pointed snouts, though rounded snouts have been observed in some individuals. Like many European common frogs, R. latastei is primarily gray or brownish red with white bellies, with almost no color variation by geographic location. The throat is dark, with a light narrow central stripe that reaches down to the chest. Some sexually active males have dark red or brown spots on their throats, orange red coloration on the underside of their thighs, and thumb pads on their forelimbs.

R. latastei is a decidedly lowland species and rarely occurs above 400 m a. s. l., only going up to the lower foothills of mountains, where the colder climate delays larval development and metamorphosis. The Italian agile frog inhabits oak and hornbeam dominated plain woods, hygrophilous woods and riparian woods characterized by white poplar and white willow trees. This types of woods may regularly be inundated by floods. It has also been reported from open habitats like wet meadows or peat bogs, as well as cottonwood plantations or ditches in agricultural areas that have sufficient vegetation. Researchers have suggested the frogs were either washed into the cave by floods – which are fairly common in most habitats preferred by the Italian agile frog – or they intentionally moved to the caves to avoid predators, find food, or seek humidity. It is unknown whether the Italian agile frog breeds in these subterranean habitats. The Italian agile frog prefers humid regions with lots of rotting plant material and remains close to rivers, streams, lakes, and other sources of freshwater, which are required for the species' breeding and reproduction. They are most active early in the morning and at dusk and tend to avoid dry weather, during which the frogs will stay closer to sources of water and reduce activity until the evening. Adults are found closer to bodies of water during the breeding season between February and April, and are more commonly found in the forests when it becomes more humid during late spring and summer. Activity tends to be highest in the summer and early autumn once the spring breeding season has concluded. Hibernation on land begins in October, and frogs will emerge in the spring to breed.

Rana latastei is endemic to the plains of northern Italy, the extreme southern tip of Switzerland, the Istrian region of Slovenia, and adjacent Croatia. In Italy, populations are reported from four regions: Lombardy, Venetia, Piedmont and Friuli Venezia Giulia, but the species is most abundant in the former two. Its distribution mainly follows the Po River plains and tributaries.

The IUCN lists this species as Vulnerable (VU). Genetic isolation is also thought to cause significant variation in size between different populations of R. latastei. The introduction of invasive predatory species – including Percottuss glenii, the American bullfrog, and crayfish – have further endangered the Italian agile frog. Tadpoles feed in an indiscriminate manner, which puts them at greater risk of ingesting these small plastic particles. Increased microplastic exposure has been associated with reduced growth, activity, and survival rates in R. latastei tadpoles. Smaller microplastic fragments have been associated with the strongest negative effects on the species. This may be because small pieces and fibers of plastic can form blockages and tangled clumps in the tadpoles' intestines. Some researchers have suggested that larger, more developed tadpoles are more resistant to the negative effects of microplastics on growth and activity. The Regione Lombardia began a conservation effort for the species between 1999 and 2001, which entailed restoration of damaged and heavily polluted ponds as well as the repatriation of tadpoles to pre existing and manmade ponds. However, these repatriation efforts were only somewhat successful because many tadpoles were placed in ponds lacking the vegetation preferred by the Italian agile frog. Human disturbances such as agriculture, water pollution, and tourism, as well as new predators in repatriated habitats like red crayfish, are additional factors that have negatively affected conservation efforts for R. latastei. A 2006 action plan by the Standing Committee of the Bern Convention called for protection and improved management of R. latastei habitats, as well as the eradication of invasive predators. Only one clutch of eggs is deposited per breeding season, typically away from areas prone to frequent flooding. There are usually between 676 and 2720 eggs in a single clutch, with an average of about 1278 eggs per clump.

Between late February and mid April, males and females gather at breeding sites, although some males have been reported to spend winters inside ponds in order to occupy an ideal breeding site before their counterparts arrive. Males arrive at the breeding sites first and attract females with a species specific call, which they repeat every 20 to 60 seconds underwater until a female arrives. Some research indicates males call not just to attract females, but also to communicate their dominance over other males within the social hierarchy. Specifically, the "mew" may primarily be used by males to attract potential mates, while the "brum" may be used for courting females or threatening rival males. It is unknown whether males of this species display other territorial behaviors towards one another, despite the high levels of competition for mates. In larger populations, it is more common for a small number of males to mate with many females. Polygyny is less frequently observed in smaller populations, suggesting there are more opportunities for male competition and breeding site monopolization in larger populations.

The Italian agile frog's primary predators include snakes, herons, pheasants, ducks, and egrets. They have also been shown to reduce activity level upon sensing the odor of dragonfly larvae, one of their most common predators. This ability to flexibly modify behavior in response to the presence of dragonflies distinguishes the Italian agile frog from other Rana species. Tadpoles also tend to metamorphosize earlier in response to invasive predators, which helps meet the energetic requirements for escaping and evading predators. However, this faster development may result in some drawbacks as well: froglets which develop faster tend to have smaller tibiofibular bones than their slower developing counterparts, likely due to the earlier time of metamorphosis. Smaller tibiofibulas – and, as a result, smaller hindlegs – impair jumping performance, so the frogs which take the longest to fully develop end up with the longest hindlegs and best jumping performance. This decreased jumping performance may make adult frogs less able to escape predators while reducing their ability to catch food.

R. latastei often shares habitats with the closely related Rana dalmatina, but does not often compete with it for resources or shelter due to having more specialized habitats and breeding behaviors. This is likely because R. latastei females which mate with R. dalmatina males fail to produce viable offspring. R. latastei tadpoles will also flexibly increase their behavior if they detect the presence of competitors – namely, R. dalmatina tadpoles, which do not modify their behavior in the presence of their R. latastei counterparts to the same degree.