Wild life (and death)

August 16, 2023 • 12:30 pm

by Greg Mayer

While Jerry’s photos of the fabulous wildlife in the Galapagos show us the marvels of life there, one thing that stood out to me when I visited the Galapagos was how frequently we came across dead animals, much more frequently than anyplace else I’ve been. This observation inspired two thoughts. First, could this abundant evidence of the struggle for existence have influenced Darwin? And, second, might the prevalence of carcasses be due to a dearth of scavengers in the depauperate biota of these islands?

On the mainlands of the Americas, there is no dearth of scavengers, two familiar ones being the Turkey Vulture (Cathartes aura) and the Black Vulture (Coragyps atratus), both found throughout the Neotropics and, for varying distances, into the United States (both) and Canada (Turkey only). Here are both of them, more or less in action.

This Turkey Vulture is standing next to a deceased Virginia Opossum (Didelphis virginiana) on a sidewalk in Oviedo, Florida.

Turkey Vulture (Cathartes aura) and Opossum (Didelphis virginiana), Oviedo, Fl, April 23, 2023.

These two Black Vultures are feeding on the carcass of a Nine-banded Armadillo (Dasypus novemcinctus), also in Oviedo, Florida. (Both of the scavenged species, opossum and armadillo, are more or less recent recent invaders from the south; the Black Vulture, too, is moving north.)

Black Vultures (Coragyps atratus) and Armadillo (Dasypus novemcinctus), Oviedo, Fl, April 24, 2023.

And here they are in action:

The Galapagos have one large raptorial bird, the Galapagos Hawk (Buteo galapagoensis), an insular derivative of Swainson’s Hawk (Buteo swainsoni). Although it hunts and eats a variety of prey, both small vertebrates and largish invertebrates, it also eats quite a bit of carrion. Darwin, in fact, thought it rather resembled caracaras, a group of hawk-like falcons that are largely scavengers, especially in its habits:

When a tortoise is killed even in the midst of the woods, these birds immediately congregate in great numbers, and remain either seated on the ground, or on the branches of the stunted trees, patiently waiting to devour the intestines, and to pick the carapace clean, after the meat has been cut away.

Jackson (1985:177) concurs:

… on every island they are also major scavengers. They will feed on virtually any dead animal. I have seen them at the carcasses of sea lions, marine iguanas, seabirds and even fish … They seem to be very fond of goat meat. … On one occasion, within five minutes of a goat being killed, thirteen birds arrived and sat within 5 m of myself and the carcass. [Invasive goats were/are being eradicated in the Galapagos by hunters employed for the purpose.]

The Galapagos Hawk, apparently, fills part of the scavenging niche filled by vultures on the mainland. It has disappeared from some islands since settlement, so its decline may account for the frequency of unscavenged carcasses. The generally dry conditions at sea level, which lead to rapid mummification, may also lead to a proliferation of unscavenged carcasses, so that Darwin, even before the hawk’s decline, may have come across them as well. I’ll have to query Jerry as to his observations in this regard.

Jackson, M.H. 1985. Galapagos: A Natural History Guide. University of Calgary Press, Calgary.

Darwin’s pet tortoise

February 12, 2014 • 4:24 pm

by Greg Mayer (addendum below)

Darwin lived in the country, and had many animals– for companionship, work, and research. For companions, his chief pets were d*gs (my favorite of Darwin’s d*gs was Bob), but he also had a tortoise that he brought home from James (Santiago) Island in the Galapagos. It has been claimed (most notably by the late Steve Irwin of Crocodile Hunter fame) that this tortoise later made its way to Australia, where it was named Harriet and lived to be about 175 years old. I always thought this story had dubious links in its chain of evidence, and Paul Chambers, in A Sheltered Life: The Unexpected History of the Giant Tortoise, after an exhausting examination, considered the story untrue.

A Galapagos tortoise from James (Santiago) Island, once owned by Charles Darwin. BM(NH) 1874.6.1.6, formerly
A Galapagos tortoise from James (Santiago) Island, once owned by Charles Darwin. BM(NH) 1874.6.1.6, formerly

Unbeknownst to me, four years ago Aaron Bauer and Colin McCarthy revealed the true fate of Darwin’s tortoise: it’s in the Natural History Museum in London, which is pretty much where you would have expected it to wind up. Henry Nicholls in the Guardian, in a Darwin Day tortoise piece, reminds us all of this fact, telling some of the details of the specimen’s history and rediscovery.

McCarthy, at the time the herpetology collection manager, found it in a store room in March of 2009, while preparing a list of Darwin specimens in the collection. Its original registration number shows it was catalogued on August 13, 1837, so it lived only a relatively short while after getting to England.

I am not at all surprised that it turned up at the Natural History Museum, nor that it was lost track of. The big, older, museums have large collections, and earlier curation policies were not up to today’s standards. There’s an old story, perhaps apocryphal, that a British paleontologist once submitted a grant application to fund an expedition to the basement of the museum!

According to Nicholls, you get to see the tortoise as part of the “Spirit Collection Tour” at the museum. “Spirit” refers not to the departed specimens’ souls, but to their method of preservation: in spirits. (Such specimens are called  “alcoholics”, which causes some initial confusion when referring to them in front of a non-museum audience).


Bauer, A.M. and C.J. McCarthy. 2010. Darwin’s pet Galápagos tortoise, Chelonoidis darwini, rediscovered. Chelonian Conservation and Biology 9:270-276. abstract

Chambers, P. 2004. A Sheltered Life: The Unexpected History of the Giant Tortoise. John Murray, London (American edition, 2006, by Oxford University Press, New York). OUP

Addendum: In response to a reader’s request, I append a photo of Bob (as well as much of the rest of the Darwin family) at Down House ca. early 1860s.

Darwin's dog Bob, lying on ground below window.
Darwin’s dog Bob, lying on ground below window.

Extinct tortoise rediscovered- sort of- and hope for Lonesome George’s clan

July 9, 2012 • 9:17 am

by Greg Mayer

The recent untimely passing of Lonesome George, the last living individual of the Galapagos tortoise subspecies from Pinta (Abingdon) Island, reminds me of a paper from earlier this year, which holds out some hope for the Pinta tortoises. In that paper, in Current Biology, Ryan Garrick and colleagues presented evidence for the continued existence of the Floreana (Charles, Santa Maria) Island tortoise. The evidence is indirect, but very interesting.

Floreana (Charles, Santa Maria) Island tortoise. Gunther 1902, plate XVI

Floreana was much visited by buccaneers and whalers, and was the first of the Galapagos islands to be colonized (in 1832). Consequently, its tortoises took it on the chin earlier than most. The last tortoises known to have been collected on the island were taken in the 1830s, and the race is supposed to have been extinct by about 1840. One of the things that made tortoises attractive to mariners was that they could survive long periods of time in the holds of ships, which sometimes led to live tortoises being brought to other islands, and, at least occasionally, their release back into the wild.

Floreana (Charles, Santa Maria) Island tortoise. Gunther 1902, plate XVII

Genetic evidence of this mixing of island tortoise populations was found by Nikos Poulalakis and colleagues. Using DNA recovered from museum specimens collected in the 19th century, Poulalakis et al. found the Floreana tortoises genetically distinctive, and that some of the Floreana genetic material was present in tortoises from the island of Isabela (Albemarle). (Michael Russello and colleagues have also found evidence of Floreana ancestry in captive tortoises.) Building on this, Garrick et al. have now shown that some of the genetically mixed tortoises on Isabela are F1 hybrids– i.e., one of their parents was a Floreana tortoise! The F1’s were also not very rare– 84 were identified– and some quite young (< 15 years), so the parents should still be around. So, a Floreana tortoise has not been found (hence the “sort of” in the title), but there’s a really good chance that they’re still out there, somewhere on Isabela. If found, they could then be bred together, and perhaps reintroduced to Floreana.

What does this mean for Lonesome George’s subspecies? Well, Michael Russello and colleagues found evidence of Pinta tortoise (that’s George’s subspecies) genetic material in Isabela tortoises, too. So, there might be a Pinta tortoise or two on Isabela as well. None of the genetically mixed tortoises have been identified as F1, though, so discovery of a living Pinta tortoise is a longer shot than finding a Floreana tortoise. But it will be very interesting to watch for the results of continued genetic surveys of Galapagos tortoises (most of the work is being carried out in the laboratory of Adalgisa Caccone at Yale), and keep our fingers crossed that Floreana and Pinta tortoises might turn up.

h/t: daveau, Dominic


Chambers, P. 2006. A Sheltered Life: The Unexpected History of the Giant Tortoise. Oxford University Press, Oxford.

Garrick, R.C., E. Benavides, M.A. Russello, J.P. Gibbs, N. Poulakakis, K.B. Dion, C. Hyseni, B. Kajdacsi, L. Marquez, S. Bahan, C. Ciofi, W. Tapia and A. Caccone. 2012. Genetic rediscovery of an ‘extinct’ Galápagos giant tortoise species. Current Biology 22: 10-11. pdf

Gunther, A. 1902. Testudo galapagoensis Novitates Zoologicae 9:184-192. BHL

Poulakakis, N., S. Glaberman, M. Russello, L.B. Beheregaray, C. Ciofi, J.R. Powell, and A. Caccone. 2008. Historical DNA analysis reveals living descendants of an extinct species of Galapagos tortoise. Proceedings of the National Academy of Sciences 105:15464-15469. pdf (not sure if it’s open access)

Russello, M.A., L.B. Beheregaray, J.P. Gibbs, T. Fritts, N. Havill, J.R. Powell and A. Caccone. 2007. Lonesome George is not alone among Galápagos tortoises. Current Biology 17: 317-318. pdf

Russello, M.A., N. Poulakakis, J.P. Gibbs, W. Tapia, E. Benavides, J.R. Powell, and A. Caccone. 2010. DNA from the past informs ex situ conservation for the future: an “extinct” species of Galápagos tortoise identified in captivity. PLoS ONE 5(1): e8683, 7 pp. pdf

Van Denburgh, J. 1914. Expedition of the California Academy of Sciences to the Galapagos Islands, 1905-1906. X. The gigantic land tortoises of the Galapagos Archipelago. Proceedings of the California Academy of Sciences (4th Ser.) 2: 203-374. pdf

An iguana appetizer

January 16, 2010 • 1:07 am

by Greg Mayer

No, it’s not a reptilian hors d’oeuvre. It’s pictures of a Galapagos land iguana, Conolophus subcristatus, to whet your appetites for those Jerry will have when he gets back. I toured the Galapagos 20 years ago, and took loads of pictures, but they’re Kodachromes (which I haven’t scanned), so the pictures of our saurian friend below are from my colleague and fellow evolutionary biologist Joe Balsano, who visisted in 2007, and then kindly regaled my Darwin class with tales and pictures of his adventure. (More Galapagos reptile photos, at the Galapagos Conservancy, here.)

The Galapagos land iguana, Conolophus subcristatus (Joe Balsano).

The first link above for the Galapagos land iguana, from the Galapagos Conservation Trust (the UK companion to the US-based Galapagos Conservancy) is slightly out of date when it says there are two species of Galapagos land iguana: there are three. The common, or just Galapagos, land iguana, Conolophus subcristatus, is shown above. The Barrington land iguana, C. pallidus, occurs only on the island of Santa Fe (also known as Barrington). The two species differ fairly subtly in color and scalation (pallidus being less colorful, with a more distinctive crest of spines; see the original description by Edmund Heller here [go to Proceedings of the Washington Academy of Sciences in the left sidebar], and the classic paper by van Denburgh and Slevin on Galapagos iguanid lizards from the California Academy Expedition here [go to Proceedings-California Academy of Sciences 4th series in the left sidebar]). These subtle differences are the sort of differences between allopatric populations (i.e., populations inhabiting distinct, nonoverlapping, geographic areas) that can lead to long and inconclusive arguments as to whether the populations should be recognized as species, or subspecies, or not named at all. These arguments are a common, and not at all unexpected, issue when dealing with organisms living on islands. (The evolutionary process issues involved, although not the taxonomic issues, are dealt with comprehensively in Jerry’s and Allen Orr’s Speciation.) But the newly discovered species the pink land iguana of Volcan Wolf on Isla Isabela (Albemarle), Conolophus marthae, is not one of these wishy-washy, is-it or is-it-not-a-species, cases: it’s a new species, alright.

The pink land iguana, Conolophus marthae. From Gentile, G., et al. 2009. An overlooked pink species of land iguana in the Galápagos. Proceedings of the National Academy of Sciences 106:507-511.

It is amply distinct, both morphologically and genetically, from the other two species, including in coloration and form of the nuchal crest, as you can see from the pictures above. But, more importantly, it is also sympatric (i.e., living together in the same place) with the common land iguana. This is important because the truest test of species status is the test of sympatry: whether two forms interbreed when they co-occur in nature. In this case, the two species live together side by side, and reproductive isolating barriers, such as differences in male behavior (see the original species description by Gabriele Gentile and Howard Snell), keep them genetically isolated from one another. (Gentile and colleagues did find a single individual which showed evidence of some genetic mixing, but it is evidently insufficient to breakdown the genetic isolation of the forms.) This is a really remarkable and exciting discovery, given how many scientists, park rangers, and even just tourists, have traversed these islands. (I have been to Isabela, not far, at least as the crow flies, from where the new species was discovered.)

Although I think it’s fair to say that interested scientists have been delighted by the discovery of the pink land iguana, a number have been disturbed by what Gentile and Snell did, or rather didn’t do, in naming the species: they did not collect a specimen to document the species, but relied upon blood samples and photos. Usually, when a new species of animal is described, a particular specimen is designated the holotype, and preserved and deposited in the collection of a museum that will make the specimen available for study by other scientists. The specific identity of the holotype fixes the application of the name, and study of the holotype helps resolve any questions or confusions concerning the status or identity of the species, as well as contributing to further knowledge of the species’ biology. But if there is no holotypic specimen, then other scientists are unable to check the describer’s claims, or test their conclusions, or advance the study of the species in any way. Gentile and Snell were aware that what they were doing was problematic, and addressed the question in their paper. They even designated a particular iguana as the holotype, but left it in the wild, hoping that at some later time it might be retrieved using a radio tag they put in it. They did not collect it out of concern that loss of even a single individual might drive the species extinct.

Alain Dubois of the Museum nationale d’Histoire naturelle and Andre Nemesio of the Universidade Federal de Minas Gerais, Brazil, have led the criticism of Gentile and Snell, while acknowledging that there may be times when it is not wise to collect a specimen. See papers by them here, here, and here; Thomas Donegan of Fundacion Proaves supports what Gentile and Snell did. In the bad old days of systematic zoology, species were often named without holotypes, and this led to much confusion. Lately, there have been several species named for which holotypes have not been collected, for the same reasons advanced by Gentile and Snell, and this has led to much controversy; many of the key papers are cited in the woks of Dubois, Nemesio, and Donegan, or in works cited therein.

Some people might ask, what’s wrong with a photo? Well, I think it should be evident that there are many things you can’t determine from a photo, but perhaps a mention of the most famous species named on the basis of a photograph will make some of the problems clear: that species is the Loch Ness monster, Nessiteras rhombopteryx (abstract only without subscription). To put it only a bit too simply, specimens are what separate zoology from cryptozoology, science from pseudoscience. More on this in a later post.

Those crazy Germans play a Darwin-related April Fool joke

April 1, 2009 • 10:02 am

An alert reader from Basel has sent me a link to an April Fool article in the Süddeutsche Zeitung, published in Munich.  It describes a new movie in which Quentin Tarantino directs Tom Cruise in a movie about the life of Charles Darwin.   Using my rough German (no time to translate the whole piece), the beginning reads:

Set visit: Cruise plays Darwin


“Like Stauffenberg [the anti-Hitler Nazi who Cruise plays in a new movie] with sideburns.”: Tom Cruise and Quentin Tarantino film Darwin’s life on the Galapagos Islands — and even make evolution palatable to creationists.

Accompanying the article is an action scene from the movie: