Diet diversity and breeding of top predators are determined by habitat stability and structure: a case study with the Eurasian otter (Lutra lutra L.)

Abstract

A study on Eurasian otter was conducted in order to establish if feeding ecology and breeding of this European freshwater top predator were affected by the habitat complexity or stability. The work was based on the comparison of contrasting environmental settings. Significant gradients were found for otter diet parameters and breeding, both also changing according to habitat gradient patterns (water capacity and permanence during droughts, habitat stability, and habitat complexity). The otter diet was less diverse in the most stable (and complex) habitats, eating more fish. Otters also breed more regularly in such more stable courses, with more suitable fish availability. The step toward lower habitat stability can put otters in a less advantageous position in front of generalist predators, foraging more frequently outside or in the edge of aquatic ecosystems. Implications for otters and other similar top predator's conservation are discussed.

Non-perennial Mediterranean rivers in Europe: Status, pressures, and challenges for research and management

“…These have shown that desiccation influences the availability of prey such as fish, which again may strongly affect the European otter (Lutra lutra) (Clavero et al, 2003;Ruiz-Olmo and Jiménez, 2009). Consequently, the mortality rate of otters increases, their abundance diminishes, and breeding success declines (e.g., Ruiz-Olmo et al, 2001).…”

New records and update on the geographic distribution of Lontra longicaudis (Olfers, 1818) (Carnivora: Mustelidae) in Seasonally Dry Tropical Forests of northeastern Brazil

“…The reduction in the amount of water during these periods also increases the risks associated with foraging, as the otters need to look for food more frequently in shallow areas or out of water, where semi-aquatic species are weaker competitors than terrestrial species, and become more vulnerable to predation and to becoming roadkill (Ruiz-Olmo et al 2001;Ruiz-Olmo & Jiménez 2008b). The reliance on ponds also makes them more vulnerable to being harassed and killed by local fishermen (Carrillo-Rubio & Lafón 2004).…”

“…Survival in unstable and harsh climate environments causes additional ecological stress to the animal (Ruiz-Olmo & Jiménez 2008b), which can be worrying if compounded with normally-tolerated environmental impacts. In these situations, otters can migrate to more stable nearby river basins (Ruiz-Olmo & Jiménez 2008a;Ruiz-Olmo & Jiménez 2008b), which may have been the cause for the absence of otters in Parnaíba freshwater ecoregion in the last 50 years. The Parnaíba River has a perennial hydrologic regime, and most of the sampled tributaries maintain water in many stretches or large ponds throughout the year.…”

The Eurasian otter Lutra lutra (Linnaeus, 1758) in Portugal

“…In Mediterranean habitats, fish availability for otters can show sharp seasonal variation, forcing it to switch on alternative prey (e.g. Magalhães et al, 2002Magalhães et al, , 2007Clavero et al, 2008;Ruiz-Olmo et al, 2009;Marques, 2010). In summer, high air temperatures and drought cause a shortage of surface waters with fish becoming confined to pool refugia and small reaches maintaining flowing waters, where they are at high risk of mortality from desiccation, predation or anoxia (Magalhães et al, 2007).…”

“…This stress factor is surely demanding for otter populations and enlarges any additional impact factor that man may impose (Beja, 1992;Matos, 1999;Basto, 2006;Ruiz-Olmo & Jiménez, 2009;Marques, 2010). Cianfrani et al (2011) assessed climate change threats to the European otter using two climate change scenarios and several forecasting approaches and climate models.…”