Dental and temporomandibular joint pathology of the island fox (Urocyon littoralis)

Museum skull specimens from 318 island foxes (Urocyon littoralis) were examined macroscopically according to predefined criteria. The study population included males (n = 129, 40.6%), females (n = 93, 29.3%) and animals of unknown sex (n = 96, 30.2%), and comprised 182 (57.2%) adults, 118 (37.1%) young adults and 18 (5.7%) individuals of unknown age, with juveniles and neonates excluded. The number of teeth present for examination was 11,438 (85.6%) with 1918 (14.4%) absent artefactually, 4 (0.03%) absent congenitally and 243 (1.82%) lost ante mortem through acquired tooth loss. There were seven persistent deciduous teeth (0.05%) in three specimens and 11 supernumerary teeth (0.08%) in 10 specimens. Teeth with extra roots were found in 38 skulls (11.9%) with 0.48% of all teeth affected. Two (0.63%) specimens had one tooth with an abnormal form. Fifty-eight (18.2%) specimens had bone fenestrations. Of the alveoli examined, 5361 (46.9%) displayed bony changes suggestive of periodontitis, with 315 (99.1%) of skulls affected. Of the teeth available for examination in 310 specimens (97.5%), most (n = 6,040, 52.8%) had some degree of attrition or abrasion. Fractures affected 1217 (11.0%) of the teeth present in 266 specimens (83.6%). Twenty-three periapical lesions (0.20%) were present in 16 skulls (5.03%). Evidence of temporomandibular joint osteoarthritis was found in seven specimens (0.02%) on either the mandibular head of the condylar process or on the mandibular fossa of the temporal bone.

Population Genetics of California Gray Foxes Clarify Origins of the Island Fox

We used mitochondrial sequences and nuclear microsatellites to investigate population structure of gray foxes (Urocyon cinereoargenteus) and the evolutionary origins of the endemic island fox (Urocyon littoralis), which first appeared in the northern Channel Islands <13,000 years ago and in the southern Channel Islands <6000 years ago. It is unclear whether island foxes evolved directly from mainland gray foxes transported to the islands one or more times or from a now-extinct mainland population, already diverged from the gray fox. Our 345 mitochondrial sequences, combined with previous data, confirmed island foxes to be monophyletic, tracing to a most recent common ancestor approximately 85,000 years ago. Our rooted nuclear DNA tree additionally indicated genome-wide monophyly of island foxes relative to western gray foxes, although we detected admixture in northern island foxes from adjacent mainland gray foxes, consistent with some historical gene flow. Southern California gray foxes also bore a genetic signature of admixture and connectivity to a desert population, consistent with partial replacement by a late-Holocene range expansion. Using our outgroup analysis to root previous nuclear sequence-based trees indicated reciprocal monophyly of northern versus southern island foxes. Results were most consistent with island fox origins through multiple introductions from a now-extirpated mainland population.

Purging of Strongly Deleterious Mutations Explains Long-Term Persistence and Absence of Inbreeding Depression in Island Foxes

The recovery and persistence of rare and endangered species are often threatened by genetic factors, such as the accumulation of deleterious mutations, loss of adaptive potential, and inbreeding depression [1]. Island foxes (Urocyon littoralis), the dwarfed descendants of mainland gray foxes (Urocyon cinereoargenteus), have inhabited California's Channel Islands for >9,000 years [2-4]. Previous genomic analyses revealed that island foxes have exceptionally low levels of diversity and elevated levels of putatively deleterious variation [5]. Nonetheless, all six populations have persisted for thousands of generations, and several populations rebounded rapidly after recent severe bottlenecks [6, 7]. Here, we combine morphological and genomic data with population-genetic simulations to determine the mechanism underlying the enigmatic persistence of these foxes. First, through analysis of genomes from 1929 to 2009, we show that island foxes have remained at small population sizes with low diversity for many generations. Second, we present morphological data indicating an absence of inbreeding depression in island foxes, confirming that they are not afflicted with congenital defects common to other small and inbred populations. Lastly, our population-genetic simulations suggest that long-term small population size results in a reduced burden of strongly deleterious recessive alleles, providing a mechanism for the absence of inbreeding depression in island foxes. Importantly, the island fox illustrates a scenario in which genetic restoration through human-assisted gene flow could be a counterproductive or even harmful conservation strategy. Our study sheds light on the puzzle of island fox persistence, a unique success story that provides a model for the preservation of small populations.

XENOTRANSFUSION IN AN ISLAND FOX (UROCYON LITTORALIS CLEMENTAE) USING BLOOD FROM A DOMESTIC DOG (CANIS LUPUS FAMILIARIS)

Successful xenotransfusion in an island fox ( Urocyon littoralis clementae) has not been previously reported but may be necessary in an emergency. An 11-yr-old male, intact, captive island fox was exhibiting clinical signs of rattlesnake envenomation including hypoperfusion, tachypnea, facial edema, and multifocal facial and cervical ecchymosis. Blood work revealed severe thrombocytopenia (18 K/μl) and anemia (Hct 15.8%). A presumptive diagnosis of rattlesnake ( Crotalus sp.) envenomation was made. Initial treatment included oxygen therapy, fluid therapy, antibiotics, antacids, pain medications, and polyvalent crotalid anti-venom. Emergency xenotransfusion using whole blood (45 ml) from a domestic dog was used due to worsening clinical signs from anemia. No acute or delayed transfusion reactions were observed in the fox and the patient made a full recovery 5 days later. Successful xenotransfusion in an island fox using whole blood from a domestic dog ( Canis lupus familiaris) is possible and may be lifesaving.

Systemic Amyloid A Amyloidosis in Island Foxes (Urocyon littoralis): Severity and Risk Factors

Systemic amyloid A (AA) amyloidosis is highly prevalent (34%) in endangered island foxes (Urocyon littoralis) and poses a risk to species recovery. Although elevated serum AA (SAA) from prolonged or recurrent inflammation predisposes to AA amyloidosis, additional risk factors are poorly understood. Here we define the severity of glomerular and medullary renal amyloid and identify risk factors for AA amyloidosis in 321 island foxes necropsied from 1987 through 2010. In affected kidneys, amyloid more commonly accumulated in the medullary interstitium than in the glomeruli (98% [n= 78 of 80] vs 56% [n= 45], respectively;P< .0001), and medullary deposition was more commonly severe (19% [n= 20 of 105]) as compared with glomeruli (7% [n= 7];P= .01). Univariate odds ratios (ORs) of severe renal AA amyloidosis were greater for short- and long-term captive foxes as compared with free-ranging foxes (ORs = 3.2, 3.7, respectively; overall P= .05) and for females as compared with males (OR = 2.9;P= .05). Multivariable logistic regression revealed that independent risk factors for amyloid development were increasing age class (OR = 3.8;P< .0001), San Clemente Island subspecies versus San Nicolas Island subspecies (OR = 5.3;P= .0003), captivity (OR = 5.1;P= .0001), and nephritis (OR = 2.3;P= .01). The increased risk associated with the San Clemente subspecies or captivity suggests roles for genetic as well as exogenous risk factors in the development of AA amyloidosis.