Chemical restraint and vasectomy in two captive Indian leopards (Panthera pardus fusca): Clinical observations and preliminary outcomes

Introduction

The Indian leopard (Panthera pardus fusca) exhibits a social structure that is both intriguing and adaptable. Although solitary by nature, these felids can peacefully coexist in social groups when sufficient space and food resources are available. However, in captive environments where space is limited and population increases due to successful breeding or the intake of rescued individuals, leopards are often housed in artificial groupings such as single-sex enclosures to control reproduction (Mallapur & Chellam, 2002; Mallapur et al., 2002) [11,12] . Such arrangements may influence their behaviour, particularly when individuals attempt to establish territories within confined exhibits (Metz et al., 2017) [14] . Conversely, housing leopards in small, compatible mixed-sex groups has been shown to reduce aggressive interactions, encourage affiliative behaviours and enhance overall enrichment in captivity (Pastorino et al., 2021) [15] . To ensure animal welfare by compatible social grouping and facilitate population management, effective birth control methods are essential. Vasectomy is one of the contraceptives that does not alter the natural behaviours or sexual dimorphism. Importantly, vasectomy is reversible, with restored fertility reported in several species, including bush dogs, chimpanzees, gorillas, Sika deer, Przewalski's horses, and lions (Silber et al., 2013; Marconi et al., 2020) [18,13] .

Materials and Methods

Two adult male Indian leopards (Panthera pardus fusca), aged six and seven years, housed at Gadag Zoo, Gadag, Karnataka, were selected for vasectomy under chemical restraint as part of a population management strategy. For identification and record-keeping, they were designated as Leopard 1 and Leopard 2, respectively. Both individuals were deemed clinically healthy upon preoperative observations, with an estimated body weight of 70 kg. The leopards were isolated from the group and fasted the day prior to surgery. Anaesthesia was induced using a combination of Xylazine (1 mg/kg body weight) and Ketamine (3 mg/kg body weight) administered via blow pipe. Additional doses of anaesthetics were given intramuscularly or intravenously as needed to maintain adequate anaesthetic depth. Vital parameters were monitored and recorded throughout the procedure at regular intervals. Once adequately immobilized, the animals were blindfolded and transferred to a makeshift operation site. Actual body weight was recorded using an electronic platform scale (Fig 1 ), and morphometric measurements were taken using a measuring tape. A thorough physical examination was conducted after positioning the leopards on the operating table. An intravenous catheter was placed in the saphenous vein to facilitate blood sampling and fluid therapy. Collected blood samples were sent for laboratory analysis within two hours. Preoperatively, Meloxicam (0.1 mg/kg IM) and long-acting Enrofloxacin (5 mg/kg IM) were administered.

For the vasectomy, the animals were placed in left lateral recumbency with the right hindlimb abducted. The surgical site around the scrotum and prepuce was aseptically prepared. Spermatic cords were palpated cranial to the scrotum, and 1 mL of 2% Lignocaine was infiltrated subcutaneously over each cord. Beginning with the left side, the spermatic cord was elevated, and the vas deferens was isolated manually. A small (0.5 cm) skin incision was made, and the vas deferens was grasped using ringed clamps through the tunica vaginalis, which was then incised and bluntly dissected. The vas deferens was occluded at two points approximately 4 cm apart using 3-0 polypropylene suture material. The lumen was near the ligatures were pierced and lumen was cauterised with thermocautery. The segment between ligatures was excised and preserved in formalin for histopathological confirmation. The cut ends were returned into the spermatic cord, and the skin incision was closed with a single interrupted suture using 2-0 polyglactin 910. Antiseptic ointment and fly repellent spray were applied to the surgical site (Fig 2 ). Following surgery, both leopards were shifted to individual enclosures. Yohimbine (10 mg IV) was administered to reverse the anaesthetic effects. The animals were closely monitored for six days in isolation before being reintroduced to their group.

Results and Discussions

The use of Xylazine and Ketamine for chemical restraint in leopards is well established and widely applied in both captive and free-ranging individuals (Belsare & Athreya, 2010; Deka et al., 2012) [3,8] . In this study, Table 1 summarizes the doses and anaesthetic durations of the Xylazine-Ketamine combination used in two adult captive male leopards undergoing elective vasectomy. The induction dose was calculated based on estimated body weight. Induction time was defined as the period from darting to complete immobilization, which was achieved within 11 minutes in Leopard 1. In Leopard 2, catatonia and head movement persisted until 20 minutes post-darting, though immobilization was sufficient to allow manual administration of supplemental anaesthetic to achieve safe restraint. Anaesthetic depth was maintained using intermittent IV boluses of Ketamine (50 mg), guided by reflex assessments. The duration of anaesthesia encompassed physical restraint, transfer to the makeshift surgical area, clinical examination, surgical intervention, post-operative relocation to the enclosure, and administration of the reversal agent Yohimbine. Leopard 2 exhibited slightly prolonged induction and recovery times compared to Leopard 1, likely due to a marginally inadequate induction dose necessitating additional anaesthetic administration to achieve the desired effect. Both animals recovered smoothly from anaesthesia.

Opportunistic physical examination during anaesthetic restraint is essential in wild animals for baseline health assessments and data collection. Both animals were in good body condition, adequately hydrated, and free of external wounds. Morphometric parameters of the leopards are shown in AI-generated images (Fig 3). Haematological results revealed inter-individual variation in WBC and differential leukocyte counts, while RBC indices and platelet values were comparable (Table 2). Serum biochemical values were largely similar between the two leopards, except for ALT, AST, and GGT, which showed marked variation (Table 3). Physiological parameters were marginally elevated in Leopard 2, possibly due to prolonged induction and associated excitation (Fig 4). Various factors like handling, environment, physiological status, management practices etc., contribute to variations in physiological parameters and our findings were within the range documented for captive leopards by Srivastav et al., 2016 [17] and Shanmugam et al., 2017 [16] . During surgery, the vas deferens within the spermatic cords was readily palpable on both sides of the prepuce. However, extracutaneous fixation using ringed clamps was difficult due to thick skin, necessitating small skin incisions to exteriorize the vas deferens. Ringed clamps proved effective for selective isolation of the vas through limited dissection.

After exteriorization of vas deference, effective occlusion is critical for vasectomy success. In human studies, cautery of the vas with fascial interposition has demonstrated lower failure rates than simple clipping and excision techniques (Barone et al., 2004; Labrecque et al., 2002) [2,10] . Given the near similar anatomy of the vas deferens across species (Dean et al., 2011) [6] , surgical techniques employed in humans may be applied in animals either to reduce the risk of spontaneous recanalization or to enable future reversal via microsurgical anastomosis (Marconi et al., 2020) [13] .

Vasectomy remains a more accessible, rapid, safe, and costeffective contraceptive option compared to hormonal or chemical alternatives (Gazendam et al., 2023) [9] . No post-operative complications such as swelling, infection, or hematoma were observed in either leopard, and no significant behavioural changes were noted. However, potential complications may include procedural failure or post-operative issues such as pseudopregnancy in females due to continued mating and copulation-induced ovulation.

Such pseudopregnancies may result in elevated progesterone exposure, with potential risks of pyometra and infertility in females (DeMatteo et al., 2006) [7] . Further investigations are required to assess these dynamics in leopard populations.

Conclusion

The Xylazine-Ketamine combination provided effective and safe anaesthetic restraint for adult male leopards undergoing physical examination and minor surgical intervention.

Vasectomy can be performed through small bilateral incisions on either side of prepuce with no immediate complications. Long-term studies are necessary to evaluate the reproductive, social, and welfare outcomes of vasectomy in captive leopard populations.

Acknowledgement

AcknowledgementThe authors wish to express their sincere gratitude to the authorities and supporting staff for their invaluable contributions to the successful and uneventful execution of the surgical procedure. Their dedication to wildlife conservation is deeply appreciated.

References

1. Adams CE, Wald M. Risks and complications of vasectomy. Urol Clin North Am. 2009;36(3):331-336.
2. Barone MA, Irsula B, Chen-Mok M, Sokal DC. Effectiveness of vasectomy using cautery. BMC Urol. 2004;4(1):10.
3. Belsare AV, Athreya VR. Use of Xylazine hydrochloride-Ketamine hydrochloride for immobilization of wild leopards (Panthera pardus fusca) in emergency situations. J Zoo Wildl Med. 2010;41(2):331-333.
4. Bertschinger HJ, de Barros Vaz Guimarães MA, Trigg TE, Human A. The use of deslorelin implants for the long-term contraception of lionesses and tigers. Wildl Res. 2008;35(6):525-530.
5. Daniel JC. The Leopard in India: A Natural History. Dehradun: Natraj Publishers; 1996. p. 228.
6. Dean EL, Kunselman AR, Cooper T, Barrantes JH, Trussell JC. Anatomical and histological equivalence of the human, canine, and bull vas deferens. Can J Urol. 2011;18(3):5699-5704.
7. DeMatteo K, Silber S, Porton I, Lenahan K, Junge R, Asa C. Preliminary tests of a new reversible male contraceptive in bush dog (Speothos venaticus): openended vasectomy and microscopic reversal. J Zoo Wildl Med. 2006;37(3):313-317.
8. Deka K, Athreya V, Odden M, Linnell J. Chemical immobilization of leopard (Panthera pardus) in the wild for collaring in Maharashtra, India. J Bombay Nat Hist Soc. 2012;109(3):153-157.
9. Gazendam BAT, Monakali OH, Landman N, Koeppel KN. A new approach to the vasectomy of African lions (Panthera leo). J S Afr Vet Assoc. 2023;94:54-58.
10. Labrecque M, Nazerali H, Mondor M, Fortin V, Nasution M. Effectiveness and complications associated with two vasectomy occlusion techniques. J Urol. 2002;168(6):2495-2498.
11. Mallapur A, Chellam R. Environmental influences on stereotypy and the activity budget of Indian leopards (Panthera pardus) in four zoos in Southern India. Zoo Biol. 2002;21:585-595.
12. Mallapur A, Qureshi Q, Chellam R. Enclosure design and space utilization by Indian leopards (Panthera pardus) in four zoos in southern India. J Appl Anim Welf Sci. 2002;5(2):111-124.
13. Marconi M, de la Torre JM, Palma C, Gallegos H, Soto E, Celis S, et al. Successful unilateral vasectomy reversal in a lion (Panthera leo). Open Vet J. 2020;9(4):322-326.
14. Metz O, Williams J, Nielsen RK, Masters N. Retrospective study of mortality in Asiatic lions (Panthera leo persica) in the European breeding population between 2000 and 2014. Zoo Biol. 2017;36(1):66-73.
15. Pastorino GQ, Brereton JE, Drago F, Mazzonetto F, Confalonieri E, Preziosi R. Investigating the effect of social grouping on the behaviour of captive leopards. J Zoo Aquar Res. 2021;9(2):116-123.
16. Shanmugam AA, Muliya SK, Deshmukh A, Suresh S, Nath A, Kalaignan P, et al. Baseline hematology and serum biochemistry results for Indian leopards (Panthera pardus fusca). Vet World. 2017;10(7):818824.
17. Shrivastav AB, Singh KP, Gupta SK. Haematobiochemical study of captive leopards. Indian J Anim Sci. 2016;86(2):174-176.
18. Silber SJ, Barbey N, Lenahan K, Silber DZ. Applying clinically proven human techniques for contraception and fertility to endangered species and zoo animals: a review. J Zoo Wildl Med. 2013;44:111-122.