Habitat selection and diet of the Neotropical otter (Lontra longicaudis) on the Osa Peninsula, Costa Rica, and range-wide monitoring recommendations

Abstract

The Neotropical otter (Lontra longicaudis) is listed as Near Threatened by the IUCN, which describes the standardization of field survey techniques and identification of key habitats as two research priorities. Basic ecological information such as habitat selection and diet is also lacking, especially in Central America. Using surveys for tracks and latrines from ten rivers on the Osa Peninsula of Costa Rica, we report results on habitat selection at the local and microhabitat scales, describe the general diet from 127 scats, and broadly discuss detection and general survey methods. We found that otters were positively associated with small-scale pastures surrounded by nearby forests at a local scale and/or negatively associated with densely forested areas. Otters further preferred deeper rivers at both local and microhabitat scales, while the availability of latrine substrates and sandbars was both important predictors of detection probability. We also deployed 12 camera traps to detect otters, and found they were much less efficient than sign surveys at determining occupancy, though our sample size is small. We conclude by proposing a methodology for standardized monitoring protocol using occupancy surveys which could be implemented across the Neotropical otter's range.

Human disturbances and the daytime activity of sympatric otters along equatorial Amazonian rivers

“…Neotropical otters showed similar patterns of diurnal river based activity across reaches with different degrees of human disturbances (boat use and with or without fishing nets). These results are not surprising as neotropical otters can be found in areas with high levels of human influence, including areas where agricultural and livestock activities occur ( Pardini & Trajano, 1999 ; Rheingantz, Santiago-Plata & Trinca, 2017 ; Rheingantz et al, 2011 ; Smith et al, 2020 ).…”

“…Such an approach enabled us to evaluate species activity in relation to variables such as boats and nets that are spatially heterogeneous across the rivers. This approach of dividing river lengths into shorter reaches (sub-sections sensu Smith et al (2020) ) has been applied previously for giant otters ( Oliveira, Norris & Michalski, 2015 ) and neotropical otters ( Smith et al, 2020 ). The decision as to the length of reaches i.e., separation distances between observations is important to avoid issues of spatial autocorrelation.…”

“…A length of 5 km corresponds (approximately) to the minimum seasonal giant otter range size of 4.6 km reported along Amazon rivers ( Evangelista & Rosas, 2011 ) and is therefore a relevant and informative scale for our understanding of the species responses. Although there are no comparable studies documenting movements or ranging of neotropical otters across Amazonia ( Camp, 2021 ), a recent study also suggests a length of 5–10 km for spatially independent registers of this species ( Smith et al, 2020 ). Additionally, a short-term (35 day) radio-telemetry study from southeastern Brazil showed a single male neotropical otter moved 1–2.6 km per day around coastal islands ( Nakano-Oliveira et al, 2004 ).…”

Characterization of shelters of the giant otter (Pteronura brasiliensis, Mammalia, Carnivora, Mustelidae) in the pantanal wetlands, state of Mato Grosso, Brazil

“…However, this important wildlife refuge as well as adjacent areas are seriously threatened by activities linked to the expanding fishing tourism along the Cuiabá River and Pantanal wetlands (Santos & Jesuz, 2014). Moreover, the contamination of the environments and aquatic biotic due to mineral exploration and the presence of mercury related to gold mining (Vieira & Alho, 2004), the exposure of sediments to pesticide residues (Possavatz et al, 2014), and construction of dams, which impede the reestablishment of migratory populations and can even permanently eliminate such populations (Smith et al, 2020), are worrisome impacts in the northern portion of the Pantanal and the basin of the Cuiabá River.…”