Health and Mortality Monitoring in Threatened Mammals: A First Post Mortem Study of Otters (Lutra lutra L.) in Italy

Abstract

Dead specimens provide valuable data for the conservation of threatened species, allowing investigations of mortality, health conditions, and demographic parameters. The Eurasian otter (Lutra lutra) is a semiaquatic carnivore listed as endangered in Italy. In 2009, we started the first post mortem (PM) study of otters in Italy, through collaborative research between mammal ecologists and veterinary pathologists, using standardized protocols. Twenty-eight otters, mostly collected between 2009 and 2017, were examined. Most otters were males (67%), between 1 and 3 years old (64%), and predominantly in good nutritional condition. Adult males were significantly larger than adult females (p < 0.02), as expected for the species, although both sexes appeared to be smaller than otters examined in Central−northern Europe. The youngest sexually mature female was 3 years old. Road traffic collisions were the major cause of death, especially in young individuals, and mainly occurred in autumn−winter, particularly for females. Investigations of the scene of death contributed to revealing factors forcing otters to travel out of the water and move over the road, suggesting appropriate measures to reduce vehicle collision risk. Other causes of death included blunt chest trauma of uncertain origin, dog and conspecific attacks, or diseases of infectious or non-infectious origin, such as ulcerative gastritis, pleuropneumonia and peritonitis. Other diagnosed diseases included lymphoma. Ecto- and endoparasites were rarely detected, although we report the first documentation of heartworm and Ixodes hexagonus infestation in Italian otters. It is important to continue comprehensive, standardized PM investigations of otters in Italy to define baseline health, biometric and demographic parameters, collect biological samples for comparative analyses, and to reduce road-kill mortality. The present study suggests that the timely collection of carcasses and collaborative and coordinated research efforts are essential for obtaining useful data for the conservation of otters.

Keywords: Eurasian otter; Italy; Lutra lutra; causes of death; health parameters; post mortem investigations; road mortality.

Figure 1

Distribution of collection sites of otters examined during the study. Abbreviations for provinces where otters were found, are showed: CH = Chieti; SA = Salerno; PZ = Potenza; MT = Matera; BA = Bari; KR = Crotone; CZ = Catanzaro; VV = Vibo Valentia.

Figure 2

Age distribution of submitted otters.

Figure 3

Uterine horns ((a) left, and (b) right) of a 7-year-old female otter showing placental scars (black arrows) and early placentations (red arrows).

Figure 4

Monthly distribution of otter road-traffic collisions (RTCs) during the study.

Figure 5

Tooth loss (a) and mandibular thickening (b) suggesting the presence of osteomyelitis in a 5-year-old male otter.

Figure 6

Lung of a female otter affected by severe fibrino-purulent pleuropneumonia: an extensive area of diffuse inflammatory infiltration is visible (HE; bar = 90 μm).

Figure 7

Otter lung showing variably extensive mineralization of bronchial cartilages: the right image shows a higher magnification of the central foci of mineralization (HE; bar = (a) 90 μm; (b) 25 μm).

Figure 8

Male otter dead due to severe gastritis: multifocal ulcerated lesions are visible on the gastric mucosa.

Figure 9

Male otter with multicentric lymphoma: monomorphic population of lymphoid cells invading the lymph node capsule (a) and the splenic parenchyma (b); (c) multifocal, moderate lymphoid infiltrations in the adrenal gland (HE; bar = (a) 50 μm; (b,c) 100 μm).