Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
It’s long been known that house cats, which are introduced to most of the places they occur (the wild members of the species are found in Europe, North Africa, and western Asia), can wreak havoc on native wildlife, perhaps the most infamous case being that of the Stephens Island Wren (Xenicus lyalli). It has often been said that the wren was exterminated by the lighthouse keeper’s cat, but the story is both a bit more complex, and much more tragic: many cats were involved, not just one, and not just the Wren, but the entire Stephens Island land bird fauna was decimated.
Stephens Island Wren (from Ibis, 1895).
A new study by Scott Loss, Tom Will and Peter Marra in Nature Communications makes new estimates of total mortality of wildlife due to house cats, and they are quite high: median estimates of 2.4 billion birds and 12.3 billion mammals annually in the United States. Money quote:
We estimate that free-ranging domestic cats kill 1.4–3.7 billion birds and 6.9–20.7 billion mammals annually. Un-owned cats, as opposed to owned pets, cause the majority of this mortality. Our findings suggest that free-ranging cats cause substantially greater wildlife mortality than previously thought and are likely the single greatest source of anthropogenic mortality for US birds and mammals. Scientifically sound conservation and policy intervention is needed to reduce this impact.
They are particularly incensed by programs that trap feral cats, but then return them to the wild after neutering them. I must say this seems to be a crazy idea– why in the world would you put the offending predators back into the ecosystem?
The most striking thing to me was their estimate that well over 2/3 of the mortality was due to “un-owned” (i.e. feral or some slight variation thereof) cats, so that cat owners taking steps to insure that their pets do not become destructive predators, while helpful, would leave most of the problem unaddressed.
Media coverage of the study can be found at the New York Times and the BBC.
Buller, W.L. 1895. On a new species of Xenicus form an island off the coast of New Zealand. Ibis 7:236-237.
Galbreath, R. & D. Brown. 2004. The tale of the lighthouse-keeper’s cat: Discovery and extinction of the Stephens Island wren (Traversia lyalli). Notornis 51:193-200. (pdf)
Loss, S.R., T. Will & P.P. Marra. 2013. The impact of free-ranging domestic cats on wildlife of the United States. Nature Communications (pdf)
Medway, D.G. 2004. The land bird fauna of Stephens Island, New Zealand in the early1890s, and the cause of its demise. Notornis 51:201-211. (pdf)
Not only did we find much commendable in Andrew Sullivan’s coverage of the pollsters vs. pundits dispute, but Andrew has now taken to posting felid pictures, too! He’s always been a diehard goggieophile.
A cat gazes upward toward cichlid fish caught in Lake Managua, Nicaragua on 26 Nov. 2012. By Hector Retamal/AFP/Getty Images.
Our felid for today is actually five felids: a mackerel (striped) tabby, a blotched tabby, a spotted cheetah, a king cheetah and a black-footed cat. In a new paper in Science by Christopher Kaelin and colleagues, the physiological basis of these pattern variations in both domestic cats and cheetahs is shown to be due to mutations at the Transmembrane aminopeptidase Q locus (Taqpep for short ) that alter the function of its encoded protein, which they call Tabulin.
Allelic variation at Tabby [mackerel (TaM) is dominant to blotched (Tab)] controls the arrangement of dark- and light-colored areas. Diagrams indicate how the distribution of black or brown eumelanin versus yellow or pale pheomelanin within individual hairs underlies the macroscopic color patterns, although in reality cat hairs frequently exhibit multiple pheomelanic bands.It has long been known that the dark areas in a tabby’s coat are places where the hairs are colored mostly by eumelanin (a darker pigment), while the hairs of the lighter areas have more phaeomelanin (a lighter pigment). In both areas, the individual hairs have bands of color (look closely at your cat’s hairs: you’ll see that few are unicolored– most are banded in some way). In mackerel tabbies, the dark and light areas are arranged in a periodic pattern, creating tiger-like stripes. This is the pattern found in the wild cats that are the domestic cat’s progenitors, and is still one of, if not the, most common patterns in domestic cats.
It has also long been known that the blotched tabby condition is due to recessive alleles at an autosomal (i.e., non sex-chromosomal) locus, called Ta, so that having two copies of the mutant allele b makes the tabby blotched. What Kaelin and colleagues have done is show that the Ta locus is in fact the gene Taqpep. In domestic cats, blotched tabbies have one (or more) of three single nucleotide mutations that alter the Tabulin protein’s function. If you have one copy of the dominant (M) allele, you’re mackerel (see diagram above).
One of the coauthors of the paper is Ann van Dyk, who, back in 1986, with R.J. van Aarde, first definitively demonstrated that king cheetahs, at one time thought to be a different species and the object of much cryptozoological speculation, were in fact a color-pattern variant of the common cheetah, with the same mode of inheritance as the blotched tabby: an autosomal recessive gene.
In the new paper Kaelin et al. extend their work to cheetahs, sequencing their Taqpep genes, and found that in king cheetahs there is a single base pair insertion in the gene that causes a frameshift, a type of mutation that alters every amino acid encoded downstream in the gene from the site of the insertion. Thus the king and blotched patterns result from alterations of a homologous gene, but the mutations themselves are not identical, being caused by a single nucleotide substitution in domestic cats but by an insertion in cheetahs.
Black-haired areas are larger, more irregular, and associated with dorsal stripes in the king cheetah.
Kaelin et al. also sequenced the Taqpep locus in 29 other species of wild cats, assessing any nonsynonymous substitution (i.e., those that change the amino-acid sequence of the protein produced by the gene) for how likely they were to alter protein function. All the cats had “normal” genes, except for the black-footed cat (Felis nigripes), which had five substitutions that were collectively judged as being very likely to alter the protein’s function. Interestingly, the black-footed cat has a pattern similar to domestic cats with a “swirled” pattern associated with the mutation T139N of the Taqpep locus:
Black-footed cat (Felis nigripes); note swirled pattern. Photo by Pierre de Chabannes pour http://www.photozoo.org.
Kaelin et al. note that blotched tabbies rarely appear in early illustrations of cats, but that by the 18th century they had become more common. They also note that there is a fairly large region (244kb of nucleotides) around the Taqpep locus that is invariant in blotched tabbies, while it has usual levels of variability in mackerel tabbies. This is the exact pattern, both historically and genetically, that we would expect if the blotched pattern had been favored by (presumably artificial) selection over the last few hundred years.
When an allele is favored by selection, closely linked forms of genes will also increase in frequency (a phenomenon known as “hitchhiking”), leading to higher frequency or fixation for a whole block of genetic material. Recombination will eventually break up the association of the favored and hitchhiking alleles, and new mutations will increase variability; but this dissociatio takes time, and until it happens the region of low variability persists as a record of the selection (which in this case may still be ongoing).
[Note by GCM: While the paper, at five pages, is long by Science‘s standards, there are still 27 pages of online supplements, and it is difficult to follow the authors’ train of argument and evidence since it requires constant switching between the paper and the appendices to fully appreciate what they’ve done (not to mention it would be impossible to do so if you were reading the journal or a reprint, rather than an online version). More justice would have been done to the authors’ work, and to their readers, had a substantially longer paper been published (which, of course, could not have appeared in Science). I mention this not to criticize the authors, but to decry the increasing practice of putting essential parts of a paper into relatively inaccessible and, I fear, ephemeral, appendices.]
Kaelin, C. B., X. Xu, L. Z. Hong, V. A. David, K. A. McGowan, A. Schmidt-Küntzel, M. E. Roelke, J. Pino, J. Pontius, G. M. Cooper, H. Manuel, W. F. Swanson, L. Marker, C. K. Harper, A. van Dyk, B. Yue, J. C. Mullikin, W. C. Warren, E. Eizirik, L. Kos, S. J. O’Brien, G. S. Barsh, and M. Menotti-Raymond. 2012. Specifying and sustaining pigmentation patterns in domestic and wild cats. Science 337:1536-1541. abstract
van Aarde, R.J. and A. van Dyk. 1986. Inheritance of the king coat colour pattern in cheetahs Acinonyx jubatus. Journal of Zoology 209: 573-578. pdf
If you can’t go, you can participate by nominating a cat video for screening at the festival. I hope some nearby WEIT reader will be able to attend and send us a report. (If it were a squid film festival, I think we know someone in Minnesota who could be relied upon.)
The cat video is the 21st century’s signature artistic form, transcending barriers of language and culture to produce an enduring record of humanity’s attempt to inaugurate an era of truly global connectivity based on the immanent, universal, and yet wholly locally-contextualized presence of the feline in all of our lives. With that in mind, here’s 43 seconds of my cat rolling around on the floor.
As a bonus felid for this weekend, I present a denizen of Darwell’s Cafe, a Long Beach, Mississippi, eatery that we’ve had occasion to note favorably before here at WEIT. While in Mississippi last week, we had dinner there, and met this fellow (a culinary report will follow).
The Unconcerned Cat at Darwell’s.
He occupied a seat at one of the outdoor tables, and as the place filled, and diners checked out his table, he looked at them disdainfully, and would not yield his seat. The singer/guitarist in the trio playing that night noted this, and announced that he was, “the most unconcerned cat on the Coast.” (“The Coast” being what this area along the Gulf of Mexico is known as.)
Today’s New York Times has an article about something I didn’t even know existed: cat agility competitions!
Anthony Hutcherson training his cat. Photo by Doug Mills/NYT.
The cats must run an obstacle course of tunnels, steps, hurdles, etc., and competitions are held at the major cat shows (which are better known for the judging of pedigreed cats; for the dog version, see Best in Show). Some cats are well trained but others “make it clear to the eager onlookers that they could not care less.”
Trainer Jill Archibald has posted a number of training videos online at Monkeysee, and also on Youtube.
If there were a box-jumping-into event, Maru might be good at it.
A number of the cats featured in the NYT article are so-called ‘Bengal cats‘, which are not domestic cats (Felis catus), but hybrids between domestic cats and leopard cats (Felis (Prionailurus) bengalensis), which have undergone several generations of breeding and selection past the F1. I’m not sure if crossing with a wild species makes them better (more agile?) or worse (harder to train?) at competing than domestic cats.
