August 16, 2022

From vaccinations to wildlife crossings and more, efforts over the past decades have shown great potential to improve the lives of wild animals. These actions usually serve a primary goal other than wild animal welfare — sometimes their intention is to reduce disease transmission to people or to conserve an endangered species.

While we don’t know yet whether these actions result in net-positive improvements for wild animal welfare, they are precedents that show wild animal welfare interventions are possible without relying on high-tech, costly methods. We aren’t necessarily calling for future applications of these specific approaches, but they offer tangible examples of what wild animal welfare improvements could look like.

Wildlife crossings and underpasses

Human structures such as roads and canals can create barriers for wild animals who want to access the full range of their habitat. Each year, millions of animals die or are injured as they attempt to cross these structures. Wildlife crossings can help wild animals by offering them bridges or underpasses that allow them to travel with less risk. 

A 2014 study in Banff National Park, Alberta, looked at crossing structures along the Trans-Canada Highway to see whether they provided genetic connectivity for two bear species. Tests revealed that 47 percent of black bears (Ursus americanus) and 27 percent of grizzly bears (Ursus arctos) who used the wildlife crossings successfully bred, thereby preventing genetic isolation. The study shows that bears living in this area use the crossing structures built for them, and further studies might reveal how this impacts lifetime welfare.

A 2019 study of the Trans-Canada highway found that wildlife crossings and fencing reduced mortality across species after mitigation, but this benefit was offset in some species through increased mortality on a nearby railroad. This tradeoff highlights the need for coordinated approaches to helping animals safely navigate their landscape.

In 2021, researchers examined the effectiveness of wildlife crossings over irrigation canals in the Piedmont forest of the Argentine Yungas. They found that 50 percent of mammalian species in the study area used the crossings, including tapeti (Sylvilagus brasiliensis), lowland tapir (Tapirus terrestris), agouti (Dasyprocta punctata), crab-eating fox (Cerdocyon thous), and tayra (Eira barbara). The researchers concluded that “the presence of both wildlife-specific and non-wildlife-specific crossings would contribute to reducing the barrier effect.”

Artificial highlands for flooding

When floods sweep into a habitat, wild animals can become lost, separated from their social groups, or drown. Flooding can kill very young animals before they’re fully mobile and is a major cause of mortality in black bear cubs. Wild animals retreat to high ground when it’s available, so in some places, people have built artificial highlands to give wild animals a place to ride out the flood. 

This paper from 2020 examines greater one-horned rhino (Rhinoceros unicornis) behavior during floods in two protected areas in Assam, India. In the paper, they say the artificial highlands “provide refuges for animals within the Kaziranga National Park, so that they do not have to leave the protected area to find safety during flood periods. Usually, groups of rhinos stay on the same highland for the duration of the high flood period, typically two to three days.”

The paper’s authors recommended that more artificial highlands or raised platforms could serve as additional refuges for the rhinos during flood events.

Contraception

Several kinds of contraceptive drugs are now on the market to reduce populations of animals traditionally considered nuisances, such as pigeons and rats. These contraceptives reduce reproductive rates, which leads to populations decreasing. Contraception is more humane than lethal control methods such as poison or spring traps, and it also could improve welfare for wild animals by reducing competition for resources and lowering parental stress. 

Earlier this year, Staff Researcher Simon Eckerström Liedholm detailed the benefits contraceptives might have for wild animal welfare and shared four project ideas for future research. Grants Manager Luke Hecht wrote about a UK plan to deliver oral contraceptives in hazelnut paste to gray squirrels (Sciurus carolinensis) as an alternative to lethal approaches.

“While further research on the welfare impacts of the contraceptive is needed,” Hecht writes, “we are optimistic about the long-term welfare benefits of sustainable populations that wildlife fertility control may facilitate. Even if this new control strategy fails to improve welfare, it could still provide crucial data to inform future efforts.”

Parasite eradication

For more than 60 years, the US Department of Agriculture has led a successful campaign to eliminate New World screwworms (Cochliomyia hominivorax), a type of fly that lays eggs in the open wounds of host people and animals. Once hatched, the larvae feed on flesh until they reach maturity. Without treatment, screwworm infestations can cause a slow and painful death from fluid loss and secondary infections. 

By breeding sterile screwworms and releasing them into the wild, USDA officials eliminated New world screwworm populations capable of sustained reproduction from North America in 1966. Highly coordinated control measures have kept reemergences from taking hold since then. The technique also presents a better option for insect welfare compared with insecticides, which might negatively impact non-target insects. 

Eradication efforts were focused primarily on benefits to people and farmed animals, but a 2016 case study from the Florida Keys illustrates how screwworm infections can take hold in wild animals and how human intervention can address infections in a wild population. 

The 2016 outbreak occurred in Key deer (Odocoileus virginianus clavium) living in Big Pine Key, Florida. Out of 875 Key deer in the area, 135 individuals died with positive or presumptive positive infestations. Multiple agencies responded to the incident, and strategies included setting up a quarantine zone, releasing sterile flies, treating infested Key deer with the anti-parasitic worm drug avermectin, and engaging the public to report suspected cases. As a result of these efforts, New World screwworms were eradicated from Big Pine Key by 2017.

Given the success of this technique, it serves as a promising model for other parasite eradication efforts. Reducing parasitic infections and the diseases they spread could improve the lives of many wild animals.

Vaccination

Vaccination campaigns, such as the one that eradicated smallpox, can prevent suffering in people and animals alike. Diseases in wild animal populations, such as rabies, present greater challenges in terms of eradication. Still, vaccination programs have succeeded at reducing transmission in wild animals, including an effort in Finland to vaccinate red foxes (Vulpes vulpes) and raccoon dogs (Nyctereutes procyonoides) using oral rabies vaccine baits. 

Researchers have explored other types of vaccines suitable for distribution to wild animals, including topical vaccines that can be spread between social species through grooming behaviors. This 2021 study demonstrated the potential for using this technique in common vampire bats (Desmodus rotundus) in Peru by using ultraviolet powder as a proxy for topical vaccines. Field experiments indicated that vaccine transfer could more than double population-level immunity compared to using conventional, non-spreadable vaccines. 

Representing another potential welfare improvement, the paper proposes this technique as an alternative to culling bats as a rabies management strategy. This could have additional benefits for other wild animals who succumb to rabies from vampire bat bites by reducing the rate of transmission between species.

Conclusion

Since we’re only beginning to investigate questions about wild animal welfare, it’s unclear whether any of these interventions would play out as expected to the net benefit of individual wild animals. Before scientists can identify methods to improve wild animal welfare, they must first understand the complexities of wild animals’ lives.

For example, an intervention that helps one kind of animal but ends up harming many other animals doesn’t actually improve overall welfare. Additionally, preventing one cause of death may lead to a different but more painful death later in life. Another consideration: If a wild animal’s life consists of mostly negative experiences, extending their life may not improve their welfare. 

With these uncertainties in mind, we can think of past actions as starting points and hone them to better address the welfare-related questions we want to answer. It’s exciting to think that improving welfare at scale could become reality very soon.