Histopathologic Evidence of Spontaneous Ovulation in Tigers (Panthera tigris)
American Association of Zoo Veterinarians Conference 2019
Megan L. Cabot1, DVM; Edward C. Ramsay1, DVM, DACZM; Deborah Chaffins3; Mee-Ja M. Sula2, DVM, DACVP
1Departments of Small Animal Clinical Sciences and 2Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA; 3Tiger Haven, Inc., Kingston, TN, USA


Spontaneous ovulation has been identified in several wild felid species, as well as in domestic cats, previously thought to undergo only induced ovulation.1,3,4 Limited studies have assessed ovulation patterns in tigers (Panthera tigris) and those have not found evidence of spontaneous ovulation in this species;2,6 however, uterine pathology typically associated with prolonged progesterone exposure has been identified in unbred tigers, suggesting spontaneous ovulation is occurring5. Ovaries from 47 tigers, previously submitted for histopathology, were reviewed. The presence or lack of corpora lutea (CL) was documented and compared with social housing condition for each animal. Social housing categories were: female housed alone; female housed with other females; female housed with one or more castrated males; and female housed with one or more intact males. Active CL were identified in 66% (10/15) of females housed alone, 85% (6/7) of females housed with other females, and 58% of females housed with a castrated male. The only female housed with an intact male did not have active CL. A chi squared test found that the presence of CL was independent of social housing condition. These results offer strong evidence of the potential for spontaneous ovulation in tigers that do not experience contact and/or breeding. This finding could impact assisted reproduction efforts as it suggests a luteal control protocol with an early luteolytic agent may have more success. It also supports spaying non-reproductive or post-reproductive female tigers to reduce the rate of uterine infections.

Literature Cited

1.  Brown JL. Comparative endocrinology of domestic and nondomestic felids. Theriogenology. 2006;66(1):25–36.

2.  Graham LH, Byers AP, Armstrong DL, Loskutoff NM, Swanson WF, Wildt DE, Brown JL. Natural and gonadotropin-induced ovarian activity in tigers (Panthera tigris) assessed by fecal steroid analysis. Gen Comp Endocrinol. 2006;147(3):362–370.

3.  Gudermuth DF, Newton L, Daels P, Concannon P. Incidence of spontaneous ovulation in young, group-housed cats based on serum and faecal concentrations of progesterone. J Reprod Fertil Suppl. 1997;51:177–184.

4.  Lawler DF, Johnston SD, Hegstad RL, Keltner DG, Owens SF. Ovulation without cervical stimulation in domestic cats. J Reprod Fertil. 1993;(Suppl. 47):57–61.

5.  McCain S, Ramsay E, Allender MC, Souza C, Schumacher J. Pyometra in captive large felids: a review of eleven cases. J Zoo Wildl Med. 2009;40(1):147–151.

6.  Seal US, Plotka ED, Smith JD, Wright FH, Reindl NJ, Taylor RS, Seal MF. Immunoreactive luteinizing hormone, estradiol, progesterone, testosterone, and androstenedione levels during the breeding season and anestrus in Siberian tigers. Biol Reprod. 1985;32(2):361–368.


Speaker Information
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Megan L. Cabot, DVM
Department of Small Animal Clinical Sciences
College of Veterinary Medicine
University of Tennessee
Knoxville, TN, USA

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