Using Wildlife Rehabilitation and Postmortem Data to Identify Key Causes of Morbidity and Mortality Impacting the Health and Welfare of Free-Living Wild Animals in Canada

Abstract

The health and welfare of wild animals are of increasing concern, yet there are very few large-scale data syntheses examining how causes of wildlife morbidity and mortality vary across time, space, and taxa. Records for 18,540 animals submitted to the Canadian Wildlife Health Cooperative (CWHC) (2009–19) and 144,846 animals admitted to 19 wildlife rehabilitation centers (WRCs) (2015–19) were evaluated to 1) identify the main causes of morbidity and mortality for Canadian wildlife and 2) assess the utility and complementarity of these two data sources to further our understanding of wildlife health. The CWHC cases (mortality) were examined by pathologists and grouped by the presence or absence of five diagnostic categories: trauma, emaciation, infection or inflammation, toxicity, and other. These CWHC animals were also classified as “killed due to real or perceived human-wildlife conflict” based on finder history. The WRC admissions were categorized by health issue (according to intake records) and based on reported or observed situational reasons for admission: parental loss, unsafe or unsuitable location, nest or habitat disturbance, illegal possession, and abnormal behavior. For both datasets, the main reason for submission or admission was trauma (44 and 48%, respectively), especially vehicle collisions (7 and 11%) and window or building strikes (5 and 7%). Many other WRC admissions were due to parental loss (28%), cat attacks (6%), and immature animals being found in unsafe or unsuitable locations (6%). Most other CWHC mortalities were caused by infections (27%) and emaciation (23%). Relatively few birds, amphibians, and reptiles submitted to CWHC were killed due to human-wildlife conflict, but 22% of mammals were killed for this reason, highlighting the taxonomic differences in the perceived threat of wildlife to finders, and therefore their response. Together, these data sources highlight key issues impacting the health and welfare of wild animals in Canada.

Trends in Admissions and Outcomes at a British Wildlife Rehabilitation Centre over a Ten-Year Period (2012–2022)

“…Traumatic injury is a common finding in animals presented to WRCs internationally, with ‘trauma’ accounting for 38.1% of WRC admissions in New York State [ 33 ]. A recent study of data both from Canadian WRCs and submissions to a national pathology service found the main reasons for admissions in both instances, 44% and 48% of admissions, respectively, to be trauma [ 69 ], illustrating the importance of trauma on both WRC admissions and truly wild populations. In this study, as in others, trauma in birds is frequently reported to be a more significant cause of morbidity and mortality than in mammals.…”

“…Several authors cite ‘collision with vehicles’ (‘hit by car’, ‘road traffic collision’, ‘vehicle impact’, etc.) as a common anthropogenic cause of trauma, accounting for between 11% of admissions across all species in a Canadian study [ 69 ], 34.7% in an Australian study [ 16 ], and 30% in Tasmania [ 38 ]. Of the known causes for rescue in New South Wales, Australia, ‘collisions with vehicles’ were the most common across all taxonomic groups, accounting for 24.3% of all cases, 20.5% for birds, and 33.5% for mammals [ 2 ].…”

“…Of the known causes for rescue in New South Wales, Australia, ‘collisions with vehicles’ were the most common across all taxonomic groups, accounting for 24.3% of all cases, 20.5% for birds, and 33.5% for mammals [ 2 ]. Window or building strikes are also commonly cited as traumatic reasons for admissions and account for 5% and 7% of admissions to a pathology service and WRCs, respectively, in Canada [ 69 ]. Collisions with buildings or windows accounted for 29.7% of the known reasons for the admission of avian casualties in Florida [ 70 ].…”

“…In a WRC in Madison, Wisconsin, dog and cat interactions accounted for 9.7% and 5.6%, respectively, of small mammal and bird admissions, with birds admitted more commonly because of cat interactions and mammals because of dog interactions [ 88 ]. In Canada, cat attacks accounted for 23% and 13% of bird and mammal admissions, respectively, in one study [ 6 ] and, more recently, 6% of overall admissions to WRCs [ 69 ]. In South Africa, dog/cat attacks accounted for 13% of admissions in both mammals and birds [ 39 ].…”

“…In foxes, species where infectious conditions might be expected to be more commonly reported, mange was only seen in 17% of red foxes, 6% had toxoplasmosis, 3% had presumed canine distemper, and 3% of rabies was reported in grey foxes [ 65 ]. A Canadian study showed that whilst significant mortalities in submissions to a wildlife pathology service were caused by infections (27%) and emaciation (23%), the same trends were not encountered in admissions to WRCs [ 69 ]. This suggests reasons for admissions to WRCs do not necessarily reflect the true reasons for morbidity and mortality in wildlife and instead reflect human–animal conflict and other contact.…”