Common coquí

Full-grown male coquís measure, from snout to vent, from 30 to 37 mm, with an average of 34 mm, while full-grown females measure from 36 to 52 mm, with an average of 41 mm. The location of the frog also effects the size, for example the higher the elevation, the larger the coquis become. The size differences between sexes are a result of additional energy consumption related to breeding behavior by males.[4]

Coquís are muddy-brown in mottled coloration on the top with rust-tan flanks and a light-gray belly. As tree frogs, Coquís possess sticky pads on the tips of their toes which help them adhere to moistened or slippery surfaces[5] They do not possess webbed feet and are not adapted to swimming.

The known lifespan of the common coquí is up to 6 years in the wild, but the majority of adults do not live past one year. It is generally thought that the species has a relatively short lifespan, with most individuals living for less than a year. In a study of the population dynamics of the common coquí, researchers found that the species has a high mortality rate, with only a small proportion of individuals surviving to reach adulthood. This high mortality is likely due to a variety of factors, including predation, disease, and competition for resources.

The common coquis are nocturnal and their behavior is influenced by the surrounding environment, specifically the moisture levels. When humidity levels rise at night they emerge and begin climbing to their homes in the canopy. As these humidity levels decrease they move back down to lower levels where the humidity is higher. The younger coqui populations live in the understory on leaves during the drier periods. The leaves are particularly common with this population because they provide protection from invaders. As they grow into adulthood, the coquis journey up to the canopy and begin the process stated above.[6]

A comparative behavioral study between frog species identified possible explanation for jump and hydration level correlations. The paper, "Water loss, cutaneous resistance, and effects of dehydration on locomotion of Eleutherodactylus frogs," examines the effects of water loss and dehydration on two species of neotropical frogs, the common coquí and the cave coquí (Eleutherodactylus cooki). The researchers found that jumping performance declined with an increase in water loss and a longer duration of exposure to dehydrating conditions. The common coquí, which occupies a wider range of habitats, including dry forests, had a slightly higher rate of water loss and lower cutaneous resistance than the cave coquí. However, these differences were not significant enough to explain the different geographic distributions of the two species. The study suggests that behavioral adaptations, rather than physiological differences, may play a role in the common coquí's ability to survive in drier habitats.[7]

Common coquís are native to the islands of Puerto Rico, Vieques and Culebra, where they are widespread and abundant; the only notable exception occurs in Puerto Rican dry forests, where the species is rarer. The common coquí is the most abundant frog in Puerto Rico, with densities estimated at 20,000 individuals/ha.[8] Densities fluctuate depending on the season and habitat. Generally, densities are higher during the latter half of the wet season and decrease during the dry season.[9] The species is considered a habitat generalist, occurring in a wide range of habitats, including mesic broadleaf forests, mountains, and urban areas, found in bromeliads, tree holes, and under trunks, rocks or trash.[10] Since the species does not require bodies of water to reproduce, they can be found on most altitudes, provided sufficient moisture is available. In Puerto Rico, they are found from sea level to a maximum of 1,200 m (3,900 ft). Adults generally tend to be found at higher altitudes than juveniles.

The common coquís are often found in cohabitation with humans. Because of their unrestricted habitat use, E. coquí can commonly be found in homes and parks. E. coquí are found in natural habitats including the human mountain forest at elevations less than 1,200 meters and in the dry forest. They are found specifically within the under story of forests at all elevations up to the canopy.[11]

The species has been introduced to Colombia,[12] Hawaii in the United States, and the Virgin Islands.[13][14] It has become a densely populated invasive species in the Hawaiian Islands, where it was accidentally introduced in the late 1980s, most likely as a stowaway on potted plants, and quickly established itself on all four major islands. It is now considered a pest species by the State of Hawaii,[15] and is on a list of 100 of the world's worst invasive alien species.[16] As an invasive species, it can reach up to 91,000 individuals/ha, almost 5 times its maximum density in its native Puerto Rico.[17] Higher densities in its invaded range are likely bolstered by a release from native predators, lack of interspecific competitors, and abundant food availability. In Hawaii, they have been found at a maximum of 1,170 m (3,840 ft) above sea level.[18] They were previously introduced in the Dominican Republic[19] and to Louisiana and Florida, but these populations have now been eradicated.

Common coquís in areas where their density exceeds 51,000/ha could consume over 300,000 invertebrates per night. Because of their large populations, Hawaii worries about both economic and ecological impacts. The common coquí currently costs this state nearly 3 million dollars a year. Its spread has been commonly through the nursery trade, and as a result many people are reluctant to buy plants from nurseries that might be infected. Those began to perform quarantines and de-infestations in order to improve their prospects. Coquis also affect real estate values in residential neighborhoods, as many refrain from buying houses where their sleep would be disturbed by the up to 73 dB call of the common coquí.[20]

Invasive management practices against the common coquí frog aim to control and reduce the population of this species in areas where it has been introduced, such as Hawaii. Preventative measures include banning the intentional transport of frogs, as well as the implementation of hot-water shower treatments on ornamental plants to kill coquí eggs, subadults, and adults. This can reduce the potential spread of the species through the trade of plants. Physical control methods, such as hand-capture, can be effective for small populations of common coquí frogs. Chemical control methods, such as the use of caffeine and water solutions, are also being tested for their efficacy in controlling the species on a larger scale. Citric acid has also been suggested as a potential control method, although its efficacy has not been demonstrated. Overall, a variety of management practices are being explored and implemented in order to control and reduce the population of common coquí frogs in invaded areas.[21]