The effect of Cats:
Unfortunately, cats do more than rounding up domoestict pests, the role we expect them to do. Their haul includes all sorts of small, indigenous animals too. In many areas lizards (including geckos and chameleons) far outnumber rats and mice.
Two student projects at UCT on cat predation around Table Mountain National Park (in the north and at the Glencairn wetlands, found that prey included a range of wild vertebrates: Shrews, Golden Moles, Geckos, Snakes and Sunbirds, among many other species. Dr Rob Simmons of the Percy Fitzpatrick Institute of African Ornithology , who supervised the research, reports that Scorpions and Baboon Spiders are also predated, and one cat nabs bats by sitting on the roof.
A Nature Communication publication estimates that free-ranging cats (pets and feral) in the USA kill 1.4-3.7 billion birds and 6.9–20.7 billion mammals annually – making cats the likely the single greatest source of anthropogenic (human-caused) mortality for US birds and mammals.
In some parts of the world, such as South Africa, owned free-ranging cats may be responsible for the highest portion of wildlife mortality. Although not driven to hunt by hunger, their higher density than feral cats, ups the numbers. (Glencairn has 300 pet cats per square kilometre!).
“Scientists knew domestic cat hunting was a significant threat to wildlife, but the Kitty Cams study, for instance, suggests that the predation rate is four-fold greater than had been thought. The Cape Town research indicates that cats in this area alone are killing between 3.9 million and 5.9 million animals each year – and I would say that’s a conservative estimate.”
Cats living on the urban edge hunt further from home and have a higher kill rate.
There are several simple measures to prevent your cat wiping out wildlife:
- Put a bell on your cat's collar. This reduces the kill rate by 50-60%.
- Get a CatBib, which interferes with their ability to pounce on prey, but not with other normal activities.
- Feed your cat regularly
- Keep your cat in at night
- Keep your cat confined to your garden. (tough on your garden fauna, but the kill area will be far smaller).
- Schedule regular play sessions: keep them entertained and exercised, and it may encourage them to stay closer to home.
- Apparently it’s possible to train most cats to walk with a harness and leash from kittenhood.
From Olivia Rose-Innes, EnviroHealth Editor http://www.health24.com/Lifestyle/Environmental-health/Animals/What-your-cat-gets-up-to-20130214
Comments
Really good journal entry, Tony. Cats are quite a touchy subject here in Texas. Several cities allow "neutered cat colonies" that are devastating to wildlife...
It's interesting to hear the passion on both sides of the issue though. I know that when I've given public programs on "Cats and Wildlife," I've been met with adversity as well as accolades for talking about the serious issue.
If you're interested, a pretty good book about the issue is called "Cat Wars" by Peter Marra:
https://www.amazon.com/Cat-Wars-Devastating-Consequences-Cuddly/dp/0691167419
This is really Magriet's project. You will see that to date, all the observations are hers.
As you say a touchy subject. So never give a talk on the topic to the spinster's club: you will be lynched. ON the other hand, bird clubs are likely to be very supportive.
Thanks for the reference. Will get me a copy ...
I trust the book mentions Darwin's theory on the number of spinsters versus the legume crop: and it is all down to the cats. More here: https://pencilandleaf.blogspot.com/2009/10/of-darwin-humble-bees-mice-cats-old.html
Ah, thank you for the correction, Tony.
Good post, Magriet! ;)
A few of the presentations I've given to the public include both the bird club AND the 'spinsters!' It can indeed be filled with passion and with people only re-affirming their preconceived notions. Ah well. We live and learn too! :)
I just started a project on iNaturalist to document feral cats in our neighbourhood.
What advice do you have for reducing the number of feral cats in an area?
Tips:
Stay humane otherwise you are heading for trouble.
Remove food sources - esp. "kind people" putting out milk and food for the 'wild' cats. Esp at holiday resourts.
Sterilize and impound.
Reintroduce higher carnivores (Caracal, Serval and Jackal and Fox, Leopards; but also Mongeese)
But this is not my field: ask at UCT or EWT or somewhere where these have been studied.
http://www.humanesociety.org/issues/feral_cats/qa/feral_cat_FAQs.html
@sambiology many thanks for this reliable source! It confirms what we were told with the TNR with the added benefit of rabies immunisation.
@tonyrebelo this FAQs is extremely helpful. It supports a trap, neuter and release back to original location, plus a dedicated caregiver who monitors, feeds and shelters the colony.
My understanding is that in most cases, TNR doesn't work. This is because new cats are introduced to the environment faster than they are being trapped; most TNR groups don't have the resources to keep up with it. Only if the supply of cats is stopped does it have any effect.
Unfortunately this has made many people cynical since TNR is the main broadly used method of controlling cats. They advocate for euthanizing cats instead, which doesn't help convince others to agree with them.
@upupa-epops that's an interesting perspective.
Is there data to support TNR not working? or under what conditions it succeeds or fails? or over what periods of time?
I will go back through my records and see what our experience adds to the picture.
I don't have an opinion, at this point, but I do want to understand.
Perhaps iNaturalist can assist in formulating the questions, and finding data supported answers.
I don't know what conditions are required; I haven't researched the issue very much. I probably should at some point...
The book Sam mentioned apparently has a chapter about TNR which might help.
Also here are a couple lists of peer-reviewed articles on the topic (with very biased commentary):
http://www.tnrrealitycheck.com/studies.asp
http://www.hahf.org/awake/tnr-not-working/
TNR advocates interpret the same papers differently:
https://www.alleycat.org/resources/key-scientific-studies-on-trap-neuter-return/
It is indeed an issue with passionate folks on both sides! In my limited experiences, TNR colonies are still totally devastating to wildlife. A neutered cat can and does still hunt birds, small mammals, and lizards... It's a touchy issue. As a wildlife biologist, I try my best to tell people about the impacts of outdoor cats, but it's ultimately the communities decision to allow or not allow the TNR or feral cat colonies.
Thank you @upupa-epops and @sambiology for the references. So TNR has a significant effect on wildlife. This is consistent with my limited experience of just over one year trying TNR. Recently, at least 3 "new" adult cats seem to be in the process of being accepted by the group.
We had not seen evidence of successful hunting for most of the first year, but that has changed in the past two months. There have been fewer sightings of Mozambican Spitting Cobras and night adders. However, that could be a matter of chance sightings, or snakes not coming so close to the house. Several weeks ago I found two dead birds in our garden, though no evidence of how they died. I'll post the photos as query cat kills. The skeletons were intact and both were on their back on open ground. It also seems that we are seeing fewer birds, especially sunbirds. This afternoon one of the cats had caught a lizard, and one of the other cats was holding the lizard by it's tail.
We appreciate all these comments and records.
The figures on the number of prey killed by domestic cats in Cape Town has ballooned since the results of our Kittycam studies were analysed. Since the video-cammed cats were seen to bring home only 18% of the prey they ct, we know the conversion factor is not 3 fold but 5.6 fold.
Hence CTs' cats nail about 27.5 million prey, 14million of which are reptiles and 450 000 birds.
The conversation factor, seen by some cat advocates as sensationilising the numbers is very similar to the only other Kittycam study in the USA, that found only 21% of prey were returned to the home. That gives a conversion factor of 4.5 fold.
Please see our paper "Caught on camera" published in Global Ecology and Conservation Seymour et al 2020, for further details on possible solutions
https://www.sciencedirect.com/science/article/pii/S2351989420307393
Abstract
Domestic cats (Felis catus) have contributed to the extinction of indigenous species worldwide, but impacts in Africa are unstudied. We compare prey returned home from three questionnaire surveys (2009, 2010 and 2013/14) in Cape Town, South Africa, with footage from some of the same cats wearing animal-borne video cameras (KittyCams), to assess differences in actual predation vs. returns.
Cape Town borders Table Mountain National Park (TMNP), so cats may prey on animals in a protected area. Urban edge (UE) and deep urban cats (DU) did not differ in predation rates, but the suite of species killed differed significantly. KittyCams revealed that most predation was nocturnal, and only 18% of prey recorded on video were returned home, thus cats kill 5.56 times more animals (averaged across all taxa) than returns data suggest.
Reptiles constituted 50% of prey, but only 17% of returns; mammals constituted 24% of prey, but 54% of returns. Non-native species represented only 6% and 17% of animals killed by UE and DU cats, respectively, pointing to a high cost of cat predation for native fauna.
Applying a correction factor of 5.56, the average domestic cat in Cape Town kills c. 90 (95% CI = 59, 123), animals.year−1. Thus, the approximately 300 000 domestic cats in Cape Town kill c. 27.5 million animals.year−1, and TMNP is likely to lose c. 203 500 animals to UE cats annually from within its boundaries.
The scale of this predation necessitates conservation options to minimise impacts of cats on wildlife, particularly near protected areas.
Thanks for posting Tony !
@tonyrebelo I've been coming across dog kill animals, mostly snakes but also the odd buck, I want to create a dog kill project in the style of this catskill project.
I'm having some trouble setting it up, could I ask advice on how to exclude/include the appropriate observations as here?
Thank you
create it, make me manager, and send me the link: I will see what the issue is.
NB: it is a traditional project - not a collections project.
https://www.inaturalist.org/projects/dog-kills-s-africa
Do you have to join before I can make you manager? I only have experience with collection projects.
Thank you
I have joined, but I dont need to be a manager. You have done fine!! Many thanks.
Great stuff, thank you for your help !
I guess the best way to get visibility of the project is just to start adding observations?
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