Prevalence of renal calculi in wolverine (Gulo gulo) from northwestern Canada

Renal calculi (kidney stones) are often reported in domestic animals and occasionally wildlife; however, prevalence is rarely reported for free-ranging wildlife. Our aim was to determine the prevalence of renal calculi in a large sample of free-ranging wolverine (Gulo gulo) from a harvested population in Yukon, Canada. We tested for an effect of sex, age, and body condition, on the presence of renal calculi. Macroscopic examination revealed renal calculi in 48 of 537 (8.9%) wolverine. Bilateralism was low, with only 6 of 48 (12.5%) affected wolverine having calculi in both kidneys. Calculi were found in similar prevalence between the sexes. A significantly higher percentage of adults (≥2 years old) had renal calculi than sub-adults (<2 years old). When considering adults alone, prevalence was 12.7% for males and 17.8% for females. The mean age of affected females was not statistically different than the sample population, but the mean age of affected adult males was 2 years older than unaffected adult males. Mean body condition scores for wolverine with and without calculi were not statistically different for females or males. Mineral composition was determined for calculi from 29 wolverine. Calculi from most wolverine (90%) were composed of 95–100% ammonium acid urate, with magnesium ammonium phosphate (struvite) and calcium phosphate (apatite) as minor (≤5%) constituents. Our study is one of the first to document the prevalence of renal calculi in a free-ranging population of wildlife. Prevalence of renal calculi in adult wolverine from northwestern Canada was substantial; however, the pathogenesis and clinical significance of nephrolithiasis in wolverine is unknown.