Simulation study compares cat population reduction methods

Is a temporary, nonsurgical contraceptive for free-roaming cats worth pursuing? How would it compare with trap-neuter-return or with cat removal in confronting overpopulation?

Research on those questions stirred dialogue at the National Council on Pet Population’s third research symposium, Nov. 15, 2015, in St. Pete Beach, Florida, where John Boone, PhD, described ongoing work by the Alliance for Contraception in Cats and Dogs in this pivotal area.

The event linked behavioral scientists sharing useful research findings with shelter professionals eager to apply them and to provide the researchers with data and suggestions for future projects.

For those who weren’t researchers, keynoter Dr. Janet Scarlett explained how to determine the quality of a study before implementing policy on the basis of research, since “not all studies are equal.” Dr. Scarlett, outgoing chair of the NCPP board of directors, is founder of Maddie’s Shelter Medicine Program and professor emerita of epidemiology at Cornell University. During the symposium, she received a certificate of appreciation for her outstanding leadership and unwavering compassion for animals.

Besides the ACC&D study, topics ranged from the pitfalls of labeling dogs in shelters as certain breeds to enhancing the welfare of cats in shelters.

A bioeconomic simulation model

Dr. Boone, a wildlife biologist, noted that the focus of his talk would be the study target—outdoor cats. As a volunteer with the ACC&D and a current board member, he has been involved in work on the population dynamics of free-roaming cats.

“What I’ll talk about is the latest manifestation of the work we’ve been doing to try to understand these targets a little better, specifically to understand how one gets the most bang from the buck when it comes to having an impact on outdoor cat populations,” he said.

The premise of the study was to reduce the number of free-roaming cats, keeping animal welfare of individual cats as the goal within the context of population medicine. From a population standpoint, it was important to know whether it was even worthwhile to develop a contraceptive. The immediate challenges in designing the study were the time and expense that would be involved and the fact that no temporary contraceptive is yet available to use in the study.

“Our resolution to this problem was virtual reality,” he said.

Virtual reality, in this case, took the form of bioeconomic stochastic simulation modeling. “The stochastic part means that, like the real world, this particular model doesn’t assume that everything’s nice and tidy; it has messiness in it and unexpected events that occur, and that’s factored into our outcome to make it more realistic,” Dr. Boone said.

The first phase of the work, the biological part of the model, resulted in publication of the article “Simulating free-roaming cat population management options in open demographic environments” in the online journal PLOS One, Nov. 26, 2014. Dr. Boone said it is a technically dense paper, but a guidance document is posted on the ACC&D website.

“To summarize the biological lessons from that work, we did learn that a temporary, three-year contraceptive like GonaCon could accomplish population control under the right set of circumstances,” Dr. Boone said.

Even if a method can work, that doesn’t automatically mean it will work, he said. The key factor is applying the method at a sufficient intensity, whether it is use of a temporary contraceptive, TNR with spay-neuter surgery, or provisional removal and euthanasia.

GonaCon is a gonadotropin-releasing hormone immunocontraceptive vaccine that was developed by the National Wildlife Research Center to provide a nonlethal option for controlling wildlife populations, according to the ACC&D website. Relative to development of a temporary contraceptive, Dr. Boone said, “The near-term thing we’re most excited about is GonaCon, which ACC&D is in the process of doing a pseudo field test on, which is a fully approved test.”

The GonaCon research is building on work by Dr. Julie K. Levy, whose much-cited paper (Theriogenology 2011;76:1517-1525) showed that a single injection of the vaccine could be an effective contraceptive for female cats for several years. Her abstract concluded “that GnRH immunocontraception is an ideal candidate for further development for feral cat control.” The ACC&D study is using a newer formulation that may have an even longer efficacy period, and the test is being conducted in a colony-type setting.

Cost and societal acceptability

Returning to the simulation study, Dr. Boone projected a slide showing cost estimates for spay-neuter surgery, euthanasia, animal holding, and nonsurgical sterilization. The economic part of the ACC&D study began with the assumption that reducing population size was the goal and with the question: What are the comparative costs to get to the same point?

The study found that nonsurgical sterilization “shines” if early efforts are sufficiently intense to reach a maintenance phase, the trapping effort is partly or fully subsidized by volunteer labor, and trapping is efficient. As with TNR, the trapping effort required to effectively manage cats will be relatively high, but the overall cost of sterilization will progressively decline as sterilization rates increase.

Dr. Boone recognized his co-authors, particularly lead author Philip S. Miller, and “modeling gurus” Aaron Anderson and Chris Slootmaker. He cited the sheltering and TNR organizations that were involved and the American Society for the Prevention of Cruelty to Animals and Merial for funding the work.

In an interview, Dr. Boone said the body of work in the PLOS One paper showed that if there were a goal to reduce a given number of cats by a given percentage in a specified time frame, it is possible to estimate and compare how many procedures that would require for each method and at what time intervals.

“But that doesn’t factor in the cost, and doing a hundred TNR procedures doesn’t cost the same as doing a hundred lethal removals, and that doesn’t cost the same as doing a hundred contraceptions. That’s where the economic model comes in: It puts cost on all of these parts of the process so we can make an economically based comparison between our options, which we couldn’t do with the PLOS paper,” he said.

We did learn that a temporary, three-year contraceptive like GonaCon could accomplish population control under the right set of circumstances.

Dr. John Boone, wildlife biologist and board member, Alliance for Contraception in Cats and Dogs, on a simulation study of free-roaming cat population management options

So, the second phase of work will be refinement of the economic model, especially to get a better handle on the costs associated with trapping cats for whatever method is used, an area where little quantitative information is available.

Dr. Boone told JAVMA that the investigators think the ACC&D simulation study went a step beyond what’s been done before in three ways. They went to greater lengths to include elements of cat population dynamics that were typically left out of simpler models. An example was factoring in the movement of cats in and out of the area instead of treating them as if they were isolated in space.

Second was their use of a software framework called Vortex, which is used for understanding the population dynamics of various species. “It has all kinds of bells and whistles and adjustable things and realistic elements that you probably wouldn’t have time to put in if you were just saying OK, this year we’re going to build a cat simulation model,” he said. “We just have to supply the particulars.”

Third, they assembled a diverse group with expertise in population dynamics and feral cats, veterinary medicine, and the humane field to define the study parameters. A thorough literature search revealed hard numbers for data such as birth and death rates of cats at various ages, but where data were lacking, the group expertise was tapped.

“The real take-home message from all of this is that many methods either may work or may not work, depending on whether the intensity and the persistence with which they’re applied are sufficient to meet the goal that you set,” Dr. Boone told JAVMA. “A lethal removal strategy can work just fine for reducing populations if you do enough of it and if you do it long enough, and TNR can work, and a temporary contraceptive can work.

“Given this reality, the debate about appropriate management strategy should really focus on factors like cost and societal acceptability.”

He continued, “Different techniques for managing cats have different requirements in terms of what’s actually sufficient for achieving a given goal. The question should be: To meet a given goal, if this is our preferred technique, are we prepared, are we able, do we understand how much of this will be enough to accomplish that goal, and are we well-prepared to go into this effort with a reasonable chance of success?”

There is nothing inherently wrong with a goal of sterilizing as many cats in a colony as possible, he said, as long as it is understood that this doesn’t necessarily achieve population size reduction.

“But if we’re in a situation where one or more parties has a vested interest in achieving population control or population size reduction, we’re dealing with a very different kind of goal, and if you don’t put in enough time and spend enough money to get over that hump and start to achieve population reduction, then you are wasting your effort and your money,” he said. “It’s not an incremental thing. You have to get up to a threshold before you even start to achieve population size reduction, so that’s the initial investment.”

Dr. Boone sees the veterinarian as “potentially a truly critical middleman” in this work.

“One of the challenges in cat population management is translating even the most fundamental messages into terms that will resonate with the people working in the field,” he said.

“Because so many veterinarians are involved in TNR programs, they’re really, as I see it, the best hope for distilling down the more technical information into terms that can be more widely implemented in the field.”

A holistic model of population dynamics

The next speaker, Tyler Flockhart, PhD, added another dimension to the discussion of free-roaming cats: a holistic model of population dynamics. Dr. Flockhart, who is with the Department of Population Medicine at the University of Guelph Ontario Veterinary College, has a wildlife ecology background. In his talk, he addressed responsible and cost-effective solutions to the urban cat overpopulation crisis.

The research by Dr. Flockhart and his colleague at OVC, Dr. Jason Coe, goes beyond the bioeconomic components in the ACC&D study to encompass all factors that can bear on outcomes with free-roaming cats, such as how a change in attitudes one way or a law can impact the whole animal-human system.

Stakeholders that must be considered in population dynamics decision-making are the animal welfare, public health, and environmental sectors. “The key is biology fits within society,” he said.

The overarching goals are to improve cat welfare, reduce euthanasia and move toward no-kill policies, reduce the unowned cat population size, mitigate impacts on the environment, and reduce the risk to public health.

The important factors to apply in his holistic model include the neuter, survival, and reproduction rates for owned, shelter, and unowned cats. For cats in transition, the model includes the rates of being reunited with owners, surrendered, adopted, abandoned, lost, or relinquished. He quoted the introduction to a paper on humane strategies for controlling feral cat populations by Drs. Julie K. Levy and P. Cynda Crawford (J Am Vet Med Assoc 2004;225:1354-1369): “The lines between loosely owned outdoor cats, tame strays, and feral cats are often blurred. … Individual cats may occupy different categories at various stages of their lives.”

Dr. Flockhart said, “The very small changes in reproductive rates and very small changes in sterilization rates of unowned cats at any point in time influence population size as a whole. Basically, (the model) allows us to rank all these rates and all these different transitions collectively at the same time to figure out the impact on different sectors. This is really important when you talk about prioritizing resources and efforts.”

He stressed that any action taken in the network reverberates through the whole system.

“First, we’re going to talk about shelter cats,” he said. “You can say that as the neuter rate of owned cats increases, the number of shelter cats decreases. As the survival rate of owned cats increases, the number of shelter cats increases.

“Next, we’re going to talk about owned cats. As the neuter rate of owned cats goes up, the number of owned cats goes down. As the survival rate of owned cats goes up, the number of owned cats goes down.”

Users of the model must input location, urban area size, and human population size. To make optimal decisions, they need to list measurable goals and objectives, which he said are often missing, along with actions, costs of the actions, how the actions influence population dynamics, a time horizon, and constraints such as financial, legal, and social.

When breed becomes a barrier

“It’s true; looks do matter,” said Lisa Gunter, a graduate student at the Canine Science Collaboratory at Arizona State University in Tempe. She talked about the effect of breed perceptions and breed labeling of dogs in shelters on attractiveness, adoptions, and length of stay for pit bull–type dogs.

Appearance is the single most important reason adopters chose their dog, she noted, citing the 2012 study “Why did you choose this pet?: adopters and pet selection preferences in five animal shelters in the United States,” by Weiss et al (Animals 2012;2:144-159).

Breed is also an important factor in adoption. In one study (Protopopova et al, 2012), fighting breeds such as pit bull–type dogs, Bulldogs, Boxers, and Shar-Peis had the lowest adoption success. Pit bull–type dogs along with Rottweilers and Chows had higher euthanasia rates in another study (Clevenger and Kass, 2003).

How dogs are labeled in terms of breed may have a lot to do with it, Gunter said. Usually, shelter staff list the breed(s) on the basis of a dog’s appearance. But a 2009 study by Voith et al comparing adoption agency breed identification with DNA breed identification of dogs found that in 87.5 percent of dogs, the breed labeling didn’t match their DNA.

Comparing photos of adult dogs labeled as pit bull–type breeds with look-alikes labeled as another breed, Gunter studied their lengths of stay. The photos were of dogs adopted from the Arizona Animal Welfare League in 2011-2014.

“Pit bulls stayed three times as long as their look-alikes,” she said.

But potential adopters at the Arizona facility in late 2013 to early 2014 who were shown those matched photos without breed labels perceived the pit bull–type dogs and the look-alikes the same in terms of attractiveness.

In another study showing videos of dogs, the pit bull–type dogs were seen as less attractive with breed labels, but without breed labels, they were rated as more attractive than the look-alikes. Breed labels for the look-alikes (such as a Labrador Retriever and a Border Collie) did not have a positive impact on attractiveness, compared with no breed label.

When Orange County Animal Services in Florida removed breed labels from all its dogs’ kennel cards and online profiles, it achieved a 72 percent increase in adoption of dogs that would have been labeled as pit bull–type dogs and a 12 percent decrease in euthanasia of those dogs, Gunter reported.

Gunter said a 1965 study by Scott and Fuller (“The genetic diversity of the dog”) demonstrated that mixed-breed dogs can show a tremendous range of physical diversity, making the premise of breed labeling moot.

“Removing labels is a low-cost option, and it could have some good outcomes for pit bulls and other breeds,” Gunter said.

Rather than “using breed labels as shorthand,” she suggested that shelter staff give adopters information they want about appearance and focus the conversation on the individual dog’s behavior.

Gunter acknowledged when asked that there is some uncharted territory, such as what a shelter can do when online sites such as Petfinder ask for breed information to list adoptable dogs, risk tracking and insurance implications, and whether the breed label would also be removed from the dog’s medical history.

Jill Perry, manager of consumer market insights for Nestle Purina PetCare, talked about the perceptions of people who avoid adopting their pet from a shelter. Her study, commissioned by Purina, focused on why some people shun shelters, exploration of an ad campaign to try and shift misperceptions and increase openness to adopting from shelters, and identifying how to overcome each barrier, with the ultimate goal of better understanding consumers so more dogs and cats can find homes.

Several main reasons account for some people’s tendency to shun shelters. Some think that most dogs and cats in shelters are mixed-breed, so shelter staff will not know what those breeds are, and finding a certain purebred dog or cat is unlikely. Others think shelters have primarily older animals, but they may want a younger one, perhaps a puppy or kitten. And some people mistakenly assume the facility will have little or no information about the animal’s health or behavioral history or pedigree.

The ad campaign proved effective, eliciting a 10 percentage point shift among those who had been considering only an animal from a breeder and a 57 percentage point shift among those who had been neutral or negative about a shelter.

“Overall, just short of a majority think a shelter is the best place to find a pet,” Perry said. There are more positive than negative perceptions about animals in shelters; it’s the consumers with negative perceptions to focus on, she said.

“Consumers are really looking for transparency,” Perry said, so it’s important to make the animal’s history available. She said what was most important to potential adopters was knowing about the shelter’s intake procedure. Make potential adopters aware that evaluations were done before the animal was cleared for adoption, emphasize the staff’s expertise, and say whether the animal gets along with children and other animals. Disclose any potential behavioral concerns and related care that was provided by veterinarians or behaviorists. And provide additional resources.

When policy or protocol becomes an obstacle

Dr. Margaret Slater and Emily Weiss, PhD, of the American Society for the Prevention of Cruelty to Animals talked about closing the door on policy-based adoptions. Dr. Slater is the senior director of veterinary epidemiology, and Dr. Weiss is vice president of research and development.

Compared with a traditional shelter setting, volunteers in a foster home might make the best adoption counselors, Dr. Weiss began. Dogs in the ASPCA Adoption Ambassadors program are placed in foster homes, and the fostering family looks for an adopter, taking the dog to public places in an “adopt me” vest and using social media. Prospective adopters benefit from detailed information about the dog’s behavior in a home.

Dr. Weiss summarized results of the AA pilot study conducted at the Louisiana Society for the Prevention of Cruelty to Animals in New Orleans and the primary study conducted at the Charleston Animal Society in Charleston, South Carolina, as reported March 24, 2014, in the online journal PLOS One.

A survey of adopters in both studies showed that the ambassadors program was effective in getting dogs adopted, and they were returned much less frequently than dogs adopted in-shelter, she said. Although length of stay was substantially longer, the dog spent that time in a foster home.

What if adoption were free? Dr. Slater related a Canadian study of cats adopted for a fee and cats whose fee was waived. The study found that in each group, 85 percent of owners took their cat for the free veterinary checkup offered, and more than 95 percent still had the cat three months later. Adopters in the fee-waived group could afford the fee but preferred free adoption; twice as many of them made a donation, and they were more likely to adopt a second fee-waived cat.

That research supports earlier research conducted by the ASPCA on fee-waived adoptions that found no difference in attachment between a group that adopted their pets with waived fees and those who paid fees.

“Owner attachment is the same with or without a fee, and waiving the fee could mean a shorter stay,” she said.

What about giving pets as gifts? Dr. Weiss cited three earlier studies, two by NCPP-affiliated researchers, that essentially found that pets obtained as gifts are rarely relinquished and in some cases are at less risk than those obtained from a shelter or friend, as a stray, or at a pet shop.

To get one more piece of data, Dr. Weiss surveyed owners who had and hadn’t received a dog or cat as a gift and found no meaningful correlation between owners who had a role in the selection, even if it was a surprise, and their love or attachment for the pet or whether it was still in their home.

Finally, Dr. Slater asked, “What happens when policies are removed and replaced with dialogue?”

She, Dr. Weiss, and co-investigators conducted a study of adopters, reported Oct. 24, 2014, in the Open Journal of Animal Sciences. Some had undergone a policy-based adoption process, others an informative conversation with shelter staff. The study found the adopters in the latter group formed the same degree of attachment to their pets, which slept on the bed in similar numbers. These adopters took the pets to a veterinarian and provided ID tags just as often and declawed with the same frequency.

Kristen Auerbach, deputy chief animal services officer of Austin Animal Center in Austin, Texas, talked about placing dogs with behavioral issues in foster homes while she was assistant director of Fairfax County Animal Shelter in Fairfax, Virginia.

Fairfax had a mean annual intake of 4,500 to 5,000 animals. Prior to 2012, the shelter was euthanizing dogs for common behavioral challenges, and there was a lengthy adoption process.

In 2013, the shelter stopped euthanizing dogs for failing a standardized behavior evaluation or for space or time limitations, and it overturned restrictions on adoption of dogs identified as pit bull–type dogs, helping communities do the same. Play groups were used to socialize dogs with other dogs and identify those with shelter-based behavioral issues.

The program placed 52 medium and large dogs of various breeds and types with 16 foster families. Each family fostered a total of one to four dogs from May 2013 to March 2015. “We agreed to give them full (behavioral) disclosure and vice versa,” she said, with support as needed.

Over 80 percent were age 3 or under, and many were “rowdy, obnoxious, and challenging,” she said. Seventeen had fear-based aggression. Secondary behavioral issues included being extremely energetic.

“In two years, we roughly doubled adoptions and cut euthanasias in half,” Auerbach said.

Thirty-three of the study dogs were adopted directly from the foster home, and 16 were taken back to the shelter and adopted. The return rate was 9.6 percent.

“This surprises people: 88 percent were in foster care less than 30 days, 40 percent of them one week or less,” Auerbach said. “Live outcomes were 90.4 percent. Had we not done this, all would have been euthanized.”

At the conclusion of the study, the fosterers shared that they thought the full disclosure better equipped them. Most didn’t witness the behavior the shelter had described. Some who did witness it said it disappeared within a week, whereas others reported a new behavior, most often separation anxiety.

In follow-up six to 18 months after adopting, 96 percent of the owners said the dog was still in their home, and the same percentage would readopt it. Most reported only typical challenges such as digging or barking. The word owners most often used to describe their once behaviorally challenged dog: “smart.”

Socializing cats to aid adoptability

Kristyn Vitale Shreve, a doctoral student and National Science Foundation graduate fellow in the Human-Animal Interaction Laboratory at Oregon State University, said that behavioral issues or cat-owner incompatibility account for at least 27 percent of the cats surrendered to shelters by owners.

Once in a shelter, dogs and cats spend more time in close proximity to an inattentive human than pets do, Vitale Shreve noted. She conducted a sociability test of 23 cats in a shelter, comprising an inattentive phase and an attentive phase of human interaction. The cats were aware of the attention or lack of attention. Meowing vocalization sometimes served as a cue that a cat was seeking human attention.

“Cats are facultatively social and display various levels of social behavior, depending on their environment and upbringing,” she said.

She said that human interaction through touch and vocalization can increase a cat’s affiliative behaviors and activity levels, cause it to seek close proximity with humans, and potentially decrease stereotypic behaviors, cortisol levels, and stress behavior.

“Cats in shelters that were given up were more stressed than strays,” she said. “You might want to focus (your efforts) first in the shelter on them.”

Vitale Shreve suggested implementing a shelter interaction protocol and enrichment activities such as providing food balls filled with treats to increase adoption rates, reduce return rates, and reduce stress-related behaviors.

The human side

Drs. Slater and Weiss also talked about a changed perspective of relinquishers and other re-homers (see JAVMA, Feb. 1, 2016, reporting on an ASPCA study that found more than a million U.S. households re-home their cats or dogs annually. What was unique was that the study looked not only at animals being re-homed to shelters but also, for example, to a friend or family member.

Dr. Sara White, executive director and veterinarian for Spay ASAP Inc., spoke on characteristics of clients and animals using nonprofit, high-volume spay-neuter clinics. She led a two-phase study funded by the ASPCA to determine whether such clinics were seeing a population different from regular veterinary clients.

Twenty-two geographically representative clinics were ultimately selected—five in the Northeast, eight in the South, five in the Midwest, and four in the West. Limitations were that data were not captured from mobile clinics, and only large clinics and English-speaking participants were included.

Dr. White said the study found that clients’ median household income was below $30,000, with 24.8 percent falling at or below the federal poverty line. Cost was the biggest factor in their choice of a nonprofit clinic. The clientele were similar among the four regions.

Most cats had never been seen by a veterinarian, and only half the dogs had. Most of the cats and one-fourth of the dogs had never been vaccinated against rabies. Of the animals that had had litters, one-third of the cats and half the dogs had had two or more litters. “Use of previous veterinary care for pets coming to clinics is much lower than in surveys of veterinary usage by the AVMA,” she said.

Dr. White said, “I hope we can use the data in promoting it being a different population.”

During the discussion period, attendee Henry Aruca, director of national marketing and corporate partnerships for VCA, commented, “This is something we look at and we’re interested in not just from a business perspective but also from the standpoint that we have a huge overpopulation problem. ... This is a dialogue that we should definitely take head-on because we’re not against pets being spayed or neutered, we’re actually for it, and however that happens, that’s a good thing. So, I think that somehow from this, we should all get together and address the issue and make sure we’re all working together.”

Related JAVMA content:

AVMA considers revising policy on feral cats (Jan. 1, 2016)

Targeted feral cat sterilization yields lower euthanasia rates (Oct. 15, 2014)

Economic study estimates costs of feral cat control (June 1, 2010)

The cat debate (Jan. 15, 2004)