The influence of riparian vegetation, woody debris, stream morphology and human activity on the use of rivers by southern river otters in Lontra provocax in Chile

Abstract

The distribution of the Endangered southern roots had the highest IRR; most of the highly marked sprainting sites were found in this habitat. Canalized river otter Lontra provocax population in southern Chile has contracted, causing concern among otter specialists rivers and streams lacking these characteristics had the lowest IRR and hardly any highly marked sprainting sites. and conservationists. The main factor contributing to this decline is the loss of suitable habitat. Because the Chilean The data indicates that otters can tolerate some degree of riparian vegetation removal, provided there is minimum Irrigation Law promotes land drainage, the removal of riparian vegetation and canalization of lowland rivers in use of floodplains by humans. Temperate evergreen ombrophilus swamp forests and shallow watercourses several provinces, this situation could deteriorate further. Using an Index of Revisitation Rate (IRR), we assessed with woody debris or gravel, riparian vegetation and a plentiful supply of macrocrustaceans appear to be the the influence of woody debris, riparian vegetation, river bank morphology and river canalization on the use of preferred habitat and conditions for the otter and may be key to its survival in freshwater habitats. rivers and streams by the southern river otter. Surveys were conducted on foot, on a monthly basis, between April 1999 and March 2001 in the south of Chile. The Keywords Chile, Lontra provocax, macrocrustaceans, otter field signs, riparian vegetation, river canalization, surveys covered 13 sections of rivers and streams, 3 km long and <50 m wide. River and stream banks with high woody debris. density of riparian vegetation, woody debris and exposed disturbance and reduce the carrying capacity of their

Population assessment and habitat use by marine otter Lontra felina in southern Chile

“…During our study, the average density of spraints collected over the total surveyed distance and the study period was lower than recorded by Medina (1998) in Andean lakes (ca 0.80 spraints/km), and that recorded by Medina et al (2003) in rivers close to this research study area (ca 1.5 spraints/km). However, if only the surveyed distance of the wetland subsystems where latrines were found is considered, the density of spraints collected was within the densities of the previously mentioned studies and higher than that recorded by Quadros & Monteiro-Filho (2001) In our study, water depth and conditions experienced during the rainy season affected the number of otter spraints found negatively.…”

“…However, depending on the habitat characteristics, the freshwater ecosystems are not all equally important (Medina-Vogel et al 2003). Previous diet studies indicate that in riverine and lacustrine wetlands, southern river otters primarily feed on invertebrates contrasting European otter Lutra lutra, American river otter Lontra canadensis, Neotropical otter L. longicaudis, giant otter Pteronura brasiliensis and spotted-necked otter Lutra maculicollis, which all feed mostly on fish (Duplaix 1980, Melquist & Hornocker 1983, Chehe´bar 1985, Chehe´bar et al 1986, Heggberget & Moseid 1994, Reid et al 1994, Carss 1995, Spinola & Vaughan 1995, Medina 1997, 1998, Taastrøm & Jacobsen 1999, Perrin & Carugati 2000, Quadros & Monteiro-Filho 2001, Medina-Vogel et al 2003. However, significant differences in prey species, including seasonal variation in the fish consumed by southern river otter, have been recorded between lakes and their river outlets, and between Andean rivers and lowland rivers (Medina 1997, MedinaVogel et al 2003.…”

“…Southern river otters use a wide range of freshwater ecosystems, ranging from deepwater Andean lakes and wide deep rivers to narrow and shallow streams, seasonal marshes and swamp forests (Chehe´bar et al 1986, Medina 1997, 1998, Medina-Vogel et al 2003, Aued et al 2003). However, depending on the habitat characteristics, the freshwater ecosystems are not all equally important (Medina-Vogel et al 2003). Previous diet studies indicate that in riverine and lacustrine wetlands, southern river otters primarily feed on invertebrates contrasting European otter Lutra lutra, American river otter Lontra canadensis, Neotropical otter L. longicaudis, giant otter Pteronura brasiliensis and spotted-necked otter Lutra maculicollis, which all feed mostly on fish (Duplaix 1980, Melquist & Hornocker 1983, Chehe´bar 1985, Chehe´bar et al 1986, Heggberget & Moseid 1994, Reid et al 1994, Carss 1995, Spinola & Vaughan 1995, Medina 1997, 1998, Taastrøm & Jacobsen 1999, Perrin & Carugati 2000, Quadros & Monteiro-Filho 2001, Medina-Vogel et al 2003.…”

“…We studied the Boroa wetland, which includes five subsystems (palustrine open water, swamp forest, permanent and seasonal marshes and open farm field) that often occur within the range of one otter home range (Medina 1996, Medina-Vogel et al 2003, Medina-Vogel 2005. The Boroa wetland complex also remains minimally altered by agriculture and pollutants from pulp factories (Hauenstein et al 2005, Marcotte 2006).…”

Use of shelters and marking sites by Lontra longicaudis (Olfers, 1818) in lotic and semilotic environments

“…The markings of other otter species as Lontra provocax (Thomas, 1908), Lutra lutra (Linnaeus, 1758) and Lontra canadensis (Schreber, 1777) are usually found in areas with less concentrated vegetation, because their visual and scent markings can be better perceived by other individuals (Madsen & Prang 2001, Medina-Vogel et al 2003. However, individuals of the L. longicaudis species, studied by MacDonald & Mason (1987) and Spinola & Vaughan (1995), most often defecate in areas with greater vertical plant cover.…”