Predators don't just kill 'prey' species; they also kill other predators whenever given the chance. Lions kill hyenas and cheetahs, tigers kill dholes, dholes kill tigers, wolves kill bears, otters kill mink... dinosaurs kill dinosaurs...
For various reasons my early plan to produce a new blog post every day has fallen by the wayside, as well it might given that this would cause me to spend what 'computer time' I have doing blog writing and nothing else. So in the interests of churning out new material, I have for a while been recycling old texts wherever possible. Several years ago, Dave Martill, Mike Barker and I collaborated on a large volume about the taphonomy of dinosaurs (taphonomy is the study of those events that occur after death). It was to be published by Johns Hopkins University Press no less. I put aside an entire year of my time as a phd student to write the book, and put loads of work into it. But for various reasons that I'd rather not discuss, the collaborative effort failed, and the book was never finished. Multiple chapters on dinosaur taphonomy were left half-finished and abandoned, and I had to give up and return to Eotyrannus and the other Wealden theropods. Most of the book's contents can't be salvaged without extensive addition and reworking, and I'm not about to do that. A few of the more interesting bits - the bits that really caught my imagination - are just about complete enough for some salvage to occur however, as the following chunk of text demonstrates. It's on intraguild predation: the fascinating phenomenon whereby predators kill other predators.
While herbivorous species are usually regarded as the ones that fall prey to predators, it is increasingly recognized by field biologists and ecologists that predators are themselves often predated upon, a phenomenon that Polis et al. (1989) termed intraguild predation. Palomares & Caro (1999) reviewed the literature on intraguild predation in mammals and listed 27 predatory species reported as having killed other predatory mammals. Many of these cases involve adults of one species killing the babies of another. However, even with these discounted there are still many notable examples.
Among extant felids, wild Felis species fall prey to jackals, wolves and dogs, Lynx may be predated upon by wolves (Kitchener 1991), pumas kill bobcats, and Lynx predates upon smaller cats, genets, mongooses and foxes. In canids, larger species kill smaller-bodied contemporaries such that wolves (20-80 kg) kill coyotes (11-15 kg) and red foxes (5-6 kg), coyotes kill red foxes and kit foxes (1.8-3 kg) and red foxes kill Arctic foxes (3-4 kg) and kit foxes. Similarly, small wild felids often kill feral house cats (Felis catus) - even those larger in size than themselves - when they encounter them. Lions kill spotted hyenas and cheetahs, tigers kill dholes, dholes kill tigers, wolves kill bears, otters kill mink, and so on and on [in the adjacent photo, the jackal obviously isn't trying to kill the hyena, but it's a good image anyway. Borrowed from here].
Intraguild predation is less well studied among birds and other non-mammalian predators but peregrines, goshawks, sparrowhawks, buzzards, hen harriers, eagle owls and tawny owls are documented as occasional or significant predators of kestrels, peregrines have been observed killing short-toed eagles, sparrowhawks and other raptors (Hammond & Pearson 1993) and both golden and white-tailed eagles reportedly kill eagle owls. Some owl species routinely kill other, smaller owls. Eagle owls (Bubo bubo) are significant killers of other owls and raptors, occasionally killing species as large as buzzards, goshawks, peregrines, gyrfalons and snowy owls (for a previous post on some of the implications of this intraguild predation see Eagle owls take over Britain).
Predation by eagle owls and goshawks was regarded by Erritzoe & Fuller (1998) as the primary factor affecting the distribution in winter of migrating Long-eared owls Asio otus. In fact predation upon carnivores by carnivores can be so significant that it may represent a serious conservation problem for endangered, localized species; it may be the dominant cause of mortality in some predator populations; and it may mean that large species can totally eradicate smaller ones on isolated islands (Macdonald 1987) or habitat pockets (Erritzoe & Fuller 1998).
The possible importance of intraguild predation has not been missed in the dinosaur literature, and theropods have often been visualized as significant dangers to other, smaller theropod species (e.g., Paul 1988). While intraguild predation surely occurred among theropods, demonstrating its occurrence from taphonomic data is another matter. Theropod tooth marks on theropod bones have been documented and may suggest intraguild predation. Naish (1999) reported a tetanuran tibia from the Lower Cretaceous Hastings Beds Group bearing theropod tooth marks, though whether these resulted from intraspecific aggression, cannibalism or intraguild predation couldn't be demonstrated.
Cannibalism has been widely suspected in theropods and reported for coelophysids and tyrannosaurids, though the baby coelophysids supposedly eaten by adult members of the same species turned out not to be baby coelophysids at all (Nesbitt et al. 2006). Definitive evidence for cannibalism has been reported for multiple specimens of the Upper Cretaceous Madagascan abelisaurid Majungasaurus* where many bones of this theropod have been discovered bearing tooth marks made by other members of the same taxon (Rogers et al. 2003). Cannibalism can be regarded as intraspecific intraguild predation.
* I ordinarily refer to this taxon as Majungatholus, as the material associated with this name is diagnostic. Conversely, the specimen associated with the older name Majungasaurus is arguably not. However, a major in-press publication on this theropod uses the name Majungasaurus, so I'll go with that.
The prevalence of intraguild predation got me wondering about those dinosaur faunas where the diversity of predatory theropods is apparently really high. I'm not talking about the Upper Cretaceous Mongolian faunas (such as those within the Djadokhta and Nemegt formations) where multiple oviraptorosaur and other taxa co-existed, as in these cases at least some of the theropods were omnivorous or herbivorous. Rather, the classic examplar is the Brazilian Santana Formation where, of the several dinosaurs known, all are theropods. In considering this unusual situation, I and colleagues (Naish et al. 2004*) wondered if these theropods might have been able to make a living by gleaning prey from the edge of the Santana lagoon (an option not available to herbivorous dinosaurs, obviously), if some of them might have been highly opportunistic and not strictly carnivorous as their morphology suggests, or if some of them might have practiced extensive intraguild predation. This is only a speculation unfortunately as we lack the relevant taphonomic data. Note that the possibility exists that theropods are over-represented in the Santana Formation due to taphonomic biases, and we discussed that possibility too.
* This is the famous paper that names the small coelurosaur Mirischia asymmetrica by the way.
The fact that intraguild predation is so prevalent among modern predators strongly indicates that this has been the case throughout history. It might be difficult to demonstrate its existence from fossils, but I think we can be very confident that theropods killed theropods, theropods killed sebecosuchians, sebecosuchians killed theropods... you get the idea.
I missed the BBC documentary on hypothetical post-Cretaceous dinosaur survival (broadcast 9pm this evening). I did catch a few bits, including Larry Witmer CT-scanning a troodontid skull. For reasons associated with personal research, I'll say that the scans looked incredibly interesting. Other than that, did I miss anything good?
Refs - -
Erritzoe, J. & Fuller, R. 1998. Sex differences in winter distribution of Long-eared owls (Asio otus) in Denmark and neighbouring countries. Vogelwarte 40, 80-87.
Hammond, N. & Pearson, B. 1993. Birds of Prey. Hamlyn, London.
Kitchener, A. C. 1991. The Natural History of the Wild Cats. Christopher Helm (London)
Macdonald, D. W. 1987. Running With the Fox. Unwin Hyman, London.
Naish, D. 1999. Theropod dinosaur diversity and palaeobiology in the Wealden Group (Early Cretaceous) of England: evidence from a previously undescribed tibia. Geologie en Mijnbouw 78, 367-373.
- ., Martill, D. M. & Frey, E. 2004. Ecology, systematics and biogeographical relationships of dinosaurs, including a new theropod, from the Santana Formation (?Albian, Early Cretaceous) of Brazil. Historical Biology 16, 57-70.
Nesbitt, S. J., Turner, A. H., Erickson, G. M. & Norell, M. A. 2006. Prey choice and cannibalistic behaviour in the theropod Coelophysis. Biology Letters 2, 611-614
Palomares, F. & Caro, T. M. 1999. Interspecific killing among mammalian carnivores. The American Naturalist 153, 492-508.
Paul, G. S. 1988. Predatory Dinosaurs of the World. Simon & Schuster, New York.
Polis, G. A., Myers, C. A. & Holt, R. D. 1989. The ecology and evolution of intraguild predation: potential competitors that eat each other. Annual Review of Ecology and Systematics 20, 297-330.
Rogers, R. R., Krause, D. W. & Curry Rogers, K. 2003. Cannibalism in the Madagascan dinosaur Majungatholus atopus. Nature 422, 515-518.
Why can't we all just get along?
For whatever reason, I stopped paying attention to the main text as soon as I read about "Majungasaurus." Now I must know why it's not being called "Majungatholus." Has the old material been shown to be a different animal? I must know!
But when I got back on track, I found a very interesting article. I wasn't aware that modern predators attacked other predators, so it was all very informative.
Do you think, loosely speaking, that predators (at least extant mammalian predators) will prey on any other predator that is smaller then itself?
In regards to the BBC documentary there was a gem of a quote by Simon Conway Morris (on my blog).
Judging by the writeup that Sarda gives the programme on her blog, I'm pretty pleased I missed it. What is it about dinosauroids... nothing for ages and all of a sudden they're everywhere (figuratively speaking).
Based on my limited observation of domestic dogs vs cats, it seems that some dogs attack cats simply because (and if) they display typical prey behavior, namely being smaller and running. Most dogs lose interest if the cat stands its ground. However, I have also seen some dogs attack cats with the obvious intent to kill it whatever its behavior. Since this is almost never initiated because of hunger, and because I have not seen the dogs actually eat the cats, I assume they attack for another reason. Competition for prey?
The program was what I've come to expect from Horizon these days. Flashy and content free. It didn't need recycled footage from "Walking with Dinosaurs". It didn't need the phoney BBC reports of "urban troodontids". The dinosauroid was introduced and shown doing its shopping, and wasn't dismissed in any serious way. If it had been I wouldn't have minded.
I also didn't like the way that the ice age was dealt with(dinosaurs would have coped and many would have migrated.) Personally I would think that maniraptorans with their feathers would have thrived and specialised.
Nice still capture from Eternal Enemies, Darren. One of my favorite NGS videos.
Mark, it depends to some extent on the individual dog. One of the primary aspects of dog-personality is known as "prey drive." Simply put, it means the dog's tendency to show predatory behavior. It varies strongly from dog to dog. A dog with a weak prey drive might not chase cats at all. One with a moderate prey drive will typically chase if the cat runs. One with a strong prey drive might well attack whatever the cat does.
As for predator-on-predator predation: The larger snakes can and do take smaller predators -- I've seen video of an anaconda eating a small caiman. And don't forget the aquatics. Sharks take dolphins, dolphins take sharks (but don't eat them), orcas take cetaceans of all sizes, including sperm whales. Crocodiles will take anything that comes within range. I wouldn't be surprised to find that there were Mesozoic marine reptiles that attacked other marine reptiles, or dinosaurs, or both. Something like Tylosaurus or Liopleurodon could certainly kill anything that crossed its path, and doubtless would take any opportunity that presented itself, even if the prey was another predator.
Wow Darren the 1yr book thing sucks. Sorry you had to suffer that.
My general rule (which I still learn the hard way from time to time, as I have a hard time saying no) is DO NOT WRITE ARTICLES FOR SCIENTIFIC VOLUMES. (Am not really preaching, am still trying to convince myself!)
Why? Big effort, typically not peer-reviewed or recognized as that important, seldom cited (or read widely) and soon forgotten, looooong delays or cancellations because editors/authors/publishers flake out and the slowest person delays the whole book, and edited volumes are generally uninteresting because they are a cobble of people's work they can't/won't publish elsewhere. There is hardly a good reason to publish in books; many more good reasons to focus energy on the primary lit (or blogs!).
The competition for prey idea is often trotted out for lion vs. cheetah agression etc. I don't see much in it, seems too costly all around.
Without human intervention, I'd guess that a dog used to feeding on wild-caught prey would readily eat any cat she killed.
Bobcats and coyotes frequently take housecats in California, almost certainly with the intent to ingest. A friend recently employed a fire-poker, to no avail, in an attempt save her cat from a hungry bobcat.
Humans kill and (eat) other predators with relish. Having tasted bobcat however, I don't recommend it even with very good relish.
A few years ago I visited Ranthanbore reserve in India, primarily to see tigers. While there I had 7 tiger sightings (one of which was very close, lasted over hald a hour and was absolutely amazing)and a single leopard sighting. The leopard was at a distance and in habitat the tigers didnt frequent. The guide told me that leopards keep well away from tigers, because the tigers will kill them if the encounter them. He stated that this was elimination of potential competition rather than predation as such, though that doesn't mean that the tiger won't eat some of the carcass.
We also saw a female nilgai which bore fresh wounds on the shoulders and flank, which the guide was certain were leopard (due to width and separation of claw marks) - he thought the leopard concerned was either inexperienced or desperate to tackle prey that was rather large for it in an area where tigers were present. Basically where leopards and tigers live in the same area, leopards keep well out of the way of tigers, usually avoiding the habitat where tigers occur, and are very elusive because they tend to occur in the marginal difficult terraine the tigers dont make use of.
I thought the general theory was that predators that prey on the same/similar species will kill each other to remove competition but generally won't eat each other unless enraged or starving, as eating a fellow predator can concentrate toxins, parasites etc. Makes good sense to me, and that seems to be the general pattern in documentary footage typically shown. Not sure though what science has been done to test this.
Studies of intraguild predation in modern mammals and birds indicate that both reasons apply: viz, some interactions occur for reasons of competition and territoriality (e.g. lions vs spotted hyenas, lions vs leopards, dholes vs tigers), whereas others are genuinely predatory in motive (e.g. lynxes vs genets, mongooses and foxes, lions vs bat-eared foxes, eagle owls vs long-eared owls). It sounds logical that eating lots of predators might be a bad idea (for the reasons mentioned by John), but - apparently - up to a third of the diet of some predators might be made up of smaller predator species. Examples includes some lynx populations and eagle owls.
Good advice on contributing to books John. I avoid doing it, otherwise I'd never get any free review copies :)
I am curious about your comment in regards to Roy Chapman Andrews not inspiring Indiana Jones. Tell me more! Where did the myth originate?
Something like Tylosaurus or Liopleurodon could certainly kill anything that crossed its path, and doubtless would take any opportunity that presented itself, even if the prey was another predator.
It would have starved otherwise, because herbivores of bigger than plankton size are few and in between in marine ecosystems, and were all but absent in jurassic/cretaceous times
At Far East Siberian (it is not correct, by the way: in Russia it is called Amur) tigers prey wolves and domestic dogs, and sometimes combat with bears. Nice example, I think.
Several years ago when Foxes in Sweden were nearly wiped out by disease the Pine Marten population literally exploded, in turn decimating e. g. Stock Doves and turning up even in agricultural habitat and wetlands where martens had never been seen before. It turns out that foxes predate young martens very heavily.
Eagle Owls will predate even ospreys and can be quite a problem for peregrines which nest in the same habitat.
Another well-known inter-guild predator is the north american Bobcat (a small Lynx) which is very fond of cats (for eating that is). The first Bobcat I ever saw was actually carrying a dead cat in its mouth.
Golden eagles are significant predators of falcons used in hunting both in the American west and in traditional Arabian falconry. Arab falconers HATE them, and I have known of about five Gyrfalcons kiled by them.
There is a nice drawing of a Goshawk with a dead Sparrowhawk by Keith Brockie in Ian Newton's Sparrowhawk monograph.
Regarding lions vs. hyaenas, specifically, I remember seeing a nature documentary a few years ago that advanced the hypothesis that some large fraction of male lions have specialized as hyaena-killers.
The reasoning goes something like: female lions in a pride don't need males around for the purposes of food-capture, as many male lions are rather crap at daylight hunting and tend to steal the best bits of any kill the females make. The females need males around for sperm, and for protection from other males who would kill all the cubs at first opportunity (paternity certainty argument goes here), but that only takes one decent-sized male, and he's going to be sleeping 22 hours per day anyway. So why do female lions tolerate males so well? Males don't practice killing herbivores, and focus on nailing hyaenas in an efficient manner - like single paw-swipe kills, only possible in a testosterone-super-charged muscular oversize male.
The documentary had some (rather impressive) footage of a fight between female lions and a group of hyaenas. Everything was going mostly the hyaenas way until an average-sized male lion showed up and rapidly killed a number of hyaenas - the slow motion footage of full-size female hyaenas getting tripped and crunched was particularly dramatic. As I remember it, after dispatching his enemies, the male promptly made some half-hearted mating attempts then went to sleep, and the females got on with hunting up dinner. The hyaenas suffered a form of social or cultural shock, as the alpha female was one of the male lion's victims, and didn't recover their dominance (or reproduction rate) in the local area for several years.
Nice post, I really enjoy these articles, thanks.
Everything was going mostly the hyaenas way until an average-sized male lion showed up and rapidly killed a number of hyaenas - the slow motion footage of full-size female hyaenas getting tripped and crunched was particularly dramatic.
Does anyone know the title of this documentary, or if it is available on VHS or DVD?
Well, to save the honour of the female gender, I have to add that male lions can be also very efficient hunters, and do not only steal prey from other predators or eat those animals which were catched by the lionesses. For example in Zaire lions developed some very unusual habits, comparable to the Savuti elephant-killers. There are no common prey species in this region like wildebeests or zebras, so the lions had to adapt their diet. There are two main prey species, with packs which are specialized on one of them, cape buffalos and hippos. Adult hippos. I read about this in a book from Vitus Droescher (a well-knwon german zoologist) which observed the attack on a hippo. The fact that they killed such a big and dangerous animal like a hippo is astonishing enough, but even more interesting was the pride of lions itself. It consisted of five unusually large males and one female, and only the males hunted, whereas the female had no part during the hunt. This social adaption is completely contradistinct to our typical imagination of lazy macho lions. In this case the strong males hunted unusual strong prey and the females acts only to give birth to youngs.
One of the problems with lions is that one size does NOT fit all: they are a highly flexible species, morphologically, ecologically and behaviourally. We mostly think of the Serengenti lions where large female prides apparently do the majority of hunting as 'typical' but they are better regarded as just part of a spectrum. In other populations, males and females contribute equally to hunting, and in others males may do the majority of hunting. As Sordes notes, this is especially the case in those populations where Cape buffalo are important prey. As I've said before, I will blog about all of this one day...
I will blog about all of this one day...
Yes please! Everything I've seen on lions also supports the hyper-labile description - variances in behaviour, within populations, within prides, within the lifespan of an individual, seem ridiculously high. Yay lions!
Sorry Dr. Vector, I do not know the name of that documentary. I think I saw it around 10 years ago, possibly as few as 8 years ago. That probably doesn't help much.