Several animal species can only be castrated through surgery, primarily because of where their testicles sit inside the body. In mammals with fully internal (intra-abdominal) testes, there is no external access point for banding, clamping, or chemical injection. Elephants, cetaceans (dolphins and whales), and certain other species fall into this category. Beyond anatomy, some animals lack approved non-surgical alternatives simply because the research and regulatory work hasn’t been done for them yet.
Why Anatomy Determines the Method
Most livestock castration alternatives, like rubber banding or chemical injection, rely on the testicles being accessible in an external scrotum. When testes are located deep inside the abdomen or high in the body cavity, these approaches are physically impossible. The only option is to go in surgically, either through a traditional incision or with laparoscopic tools inserted through small openings in the abdominal wall.
Elephants
Both African and Asian elephants have fully internal testes located deep in the abdomen, close to the kidneys. There is no scrotum and no external access. Castration or sterilization requires laparoscopic surgery performed under general anesthesia, which in a five-ton animal is itself a major undertaking. In practice, most population control efforts in elephants have used vasectomy rather than full castration, because removing the testes from that depth carries substantial risk. A study of 45 free-ranging African savannah elephants demonstrated that laparoscopic vasectomy could be performed in the field, though complications included intestinal lacerations and one death within 24 hours of recovery. The procedure required specialized slings to position the animals and carried risks of nerve damage from the support equipment alone.
Dolphins, Whales, and Other Cetaceans
Cetaceans also carry their testes entirely inside the body. This is an adaptation to aquatic life: external testes would create drag and be vulnerable to injury. The internal placement, combined with a thick blubber layer and the difficulty of performing surgery on an animal that must remain in or near water, makes castration exceptionally challenging. Laparoscopic techniques can overcome some of the anatomical barriers that make traditional open surgery nearly impossible in these species, but environmental constraints (keeping the animal stable, managing wound healing in a marine environment) add layers of complexity that don’t exist with land mammals.
Horses, Donkeys, and Mules
Equines are the most commonly castrated large animals that still require surgery as the standard method. No chemical castration product is approved for stallions, and hormonal approaches have not proven reliable enough for routine use. The Canadian Veterinary Medical Association describes equine castration as a surgical procedure that poses significant welfare risks, particularly in mature animals. Horses are routinely castrated at up to two years of age, substantially older than other farmed species, which increases the risk of complications including serious blood loss, infection, and in rare cases, evisceration.
Complicating matters, some equines are cryptorchid, meaning one or both testicles remain inside the abdomen or inguinal canal rather than descending into the scrotum. In horses, donkeys, and mules, the testicles may not descend until weeks or months after birth, and in some individuals they never do. Cryptorchid animals require abdominal surgery, sometimes laparoscopic, to locate and remove the retained testicle. This is true regardless of species: any cryptorchid animal that needs castration will need surgery, because there is simply nothing external to work with.
Sugar Gliders and Small Exotic Mammals
Sugar gliders are a common example of a small pet species with no approved non-surgical sterilization option. Males are castrated through a procedure called orchiectomy with scrotal ablation, performed under gas anesthesia. The entire scrotal sac is removed along with the testes to prevent the pouch-like scrotum from becoming a source of self-mutilation or infection afterward. Techniques range from traditional suture ligation to carbon dioxide laser and tissue fusion devices, but all are surgical. The same is true for hedgehogs and many other small exotic mammals kept as pets: the market is too small for pharmaceutical companies to pursue regulatory approval for chemical alternatives.
Cryptorchid Animals Across All Species
Cryptorchidism creates a surgical-only situation in any species, even those that normally have straightforward external castration options. A dog, cat, pig, or horse with a retained testicle cannot be banded, clamped, or chemically treated because the testicle is hidden inside the body. In humans, untreated cryptorchidism carries a 1% decrease in fertility for every six months of delay, a 5% increased need for assisted reproduction, and a 6% increased risk of testicular cancer. The pattern in animals is similar: retained testes are at higher risk for torsion and cancer, making surgical removal important rather than optional. Hormonal therapy to encourage descent has low response rates and lacks long-term efficacy, so surgery remains the recommended intervention.
Why Non-Surgical Options Remain Limited
Chemical and immunological sterilization products do exist for some species. Immunocontraceptive vaccines have been used in wildlife management, and a company called Epivara has patented a non-surgical sterilization technology for dogs, cats, and boars that is currently seeking FDA and USDA approval. But even where these products eventually reach the market, they won’t help species whose testes are inaccessible by design. Elephants, cetaceans, and other animals with intra-abdominal testes will always require a surgical approach, because the fundamental constraint is anatomical rather than pharmacological. For equines, small exotics, and cryptorchid individuals of any species, surgery remains the only proven and available method today.