Birth control at the zoo

December 20, 2013

Common hippopotami (Hippopotamus amphibius) are vulnerable to extinction in the wild, but reproduce extremely well under captive breeding conditions. Females can give birth to up to 25 young over their 40 year lifespan - evidently too many for zoos to accommodate. Captive populations of hippopotamus must therefore be controlled. Male castration is useful in this respect because it can simultaneously limit population growth and reduce inter-male aggression. However, documented cases of successful hippo castrations are scant. The procedure is notoriously difficult due to problems with anaesthesia and difficulties in locating the testes.

Physiological adaptations to life in the water

Hippos are well adapted to an aquatic lifestyle (indeed they are distantly related to whales and other cetaceans), and this is reflected in peculiar physical and physiological features. While whales have truly internal testes that remain in the abdomen at all times, hippos "hide" them in the inguinal canal, a passage in the frontal abdominal wall. Thus the testes are externally difficult to locate by sight or touch. A team supporting Chris Walzer from the Research Institute of Wildlife Ecology of the Vetmeduni Vienna as well as colleagues from three zoological institutions and the Leibniz Zoo for Zoo and Wildlife Research (IZW) evaluated surgical castration in ten adult common hippopotami held at various zoos. Walzer and colleagues had previously developed a successful hippo anaesthesia protocol, a challenge in itself, because delivery of sufficient anaesthetic is hampered by the hippo's thick skin and dense subcutaneous tissue. Also, the anaesthetics can cause breathing irregularities and sometimes even death.

Retracting tricks

All animals in the study were anaesthetized with close monitoring of the vital functions. The testes were located using ultrasound. Locating the testes once, however, is not sufficient, as they are sometimes retracted following incision, making intra-surgical ultrasound location necessary. "We used an adapted version of a castration technique commonly used for horses", explains Walzer. "In horses location is easier, because they have an external scrotum, but in hippos you cannot really see anything. We had not seen any previous reports of the use of ultrasound for locating the testicles, but this proved essential, because the location of the testes is highly variable and can change from one moment to the next." All surgery and ligations had to be performed under conditions of extremely low visibility and with difficulty of mobilizing and grasping the elusive testicles.

Resilient heavyweights

Like their whale cousins, hippos have excellent wound healing which is not surprising, given that they often injure one another in fights and would otherwise succumb to bacterial wound infections in an aquatic environment. This is based on the secretion of a red sweat, with antibiotic-like properties. Following surgery, the hippos were simply returned to their respective pools with no ill-effects to wound healing.
-end-
The article "Surgical castration of the male common hippopotamus (Hippopotamus amphibius)" by Christian Walzer, Thierry Petit, Gabrielle L. Stalder, Igal Horowitz, Joseph Saragusty, and Robert Hermes is published in the journal Theriogenology. http://www.sciencedirect.com/science/article/pii/S0093691X13004275

About the University of Veterinary Medicine, Vienna

The University of Veterinary Medicine, Vienna is the only academic and research institution in Austria that focuses on the veterinary sciences. About 1200 employees and 2300 students work on the campus in the north of Vienna, which also houses the animal hospital and various spin-off-companies. http://www.vetmeduni.ac.at

Scientific Contact:

Prof. Chris Walzer
Research Institute for Wildlife Ecology
University of Veterinary Medicine Vienna (Vetmeduni Vienna)
T +43 1 48909150-180
chris.walzer@vetmeduni.ac.at

Released by:

Susanna Kautschitsch
Science Communication / Public Relations
University of Veterinary Medicine Vienna (Vetmeduni Vienna)
T +43 1 25077-1153
susanna.kautschitsch@vetmeduni.ac.at

University of Veterinary Medicine -- Vienna

Related Ultrasound Articles from Brightsurf:

An integrated approach to ultrasound imaging in medicine and biology
Announcing a new article publication for BIO Integration journal. In this editorial, Co-Editor-in-Chief, Pingtong Huang considers an integrated approach to ultrasound imaging in medicine and biology.

PLUS takes 3D ultrasound images of solids
A two-in-one technology provides 3D images of structural defects, such as those that can develop in aircraft and power plants.

Scientists develop noninvasive ultrasound neuromodulation technique
Researchers from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences developed a noninvasive ultrasound neuromodulation technique, which could potentially modulate neuronal excitability without any harm in the brain.

World's first ultrasound biosensor created in Australia
Most implantable monitors for drug levels and biomarkers invented so far rely on high tech and expensive detectors such as CT scans or MRI.

Ultrasound can make stronger 3D-printed alloys
A study just published in Nature Communications shows high frequency sound waves can have a significant impact on the inner micro-structure of 3D printed alloys, making them more consistent and stronger than those printed conventionally.

Full noncontact laser ultrasound: First human data
Conventional ultrasonography requires contact with the patient's skin with the ultrasound probe for imaging, which causes image variability due to inconsistent probe contact pressure and orientation.

Ultrasound aligns living cells in bioprinted tissues
Researchers have developed a technique to improve the characteristics of engineered tissues by using ultrasound to align living cells during the biofabrication process.

Ultrasound for thrombosis prevention
Researchers established real-time ultrasonic monitoring of the blood's aggregate state using the in vitro blood flow model.

Ultra ultrasound to transform new tech
A new, more sensitive method to measure ultrasound may revolutionize everything from medical devices to unmanned vehicles.

Shoulder 'brightness' on ultrasound may be a sign of diabetes
A shoulder muscle that appears unusually bright on ultrasound may be a warning sign of diabetes, according to a new study.

Read More: Ultrasound News and Ultrasound Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.