Zoology has a discipline: evolution; zoology is vertically integrated, concerned with biological organisation at the level of organisms in their environment, organs, tissues, cells and molecules. This blog meanders through the animal kingdom, from aardvarks and anoles, through mouse and man, to zorillas and zebras.
This photograph I came across connects three topics I have written about before:
Dr Burgess Barnett shortly after taking over as Curator of Reptiles at London Zoo. I have found it difficult to find photographs of him and I will add this to the article on his life and works. The article here on Barnett, incidentally, is one of the most popular on this site.
Lord Moyne (Walter Edward Guinness, 1880-1944) back from an earlier expedition cruise than the one in 1934-35 in which he brought back Komodo dragons. That trip was well documented but the earlier one was not. Article can be found here.
Galapagos Marine Iguanas. Four collected by the Moyne Expedition being handed over to London Zoo. Article on Marine Iguanas in captivity here.
I have been unable to find find the name of the yacht Moyne used in 1932 since he seemed to have owned two at the time, both were converted passenger vehicles. My guess it was the MYRoussalka since she had tanks fitted during conversion to hold sufficient diesel fuel to cross the Pacific. Many of Moyne’s records were lost when the vessel sank after striking a rock in Killary Bay, Ireland, in 1933. That may account for the lack of information. All the passengers and crew, including Moyne, escaped.
Four Marine Iguanas were brought back by Moyne. A discussion on the ZooChat forum some time ago, notes that they were mentioned in the 1933 Zoo Guide with the statement that seaweed was brought up from Cornwall to feed them. One only was noted in 1934 and all mention had disappeared by 1935. So far I have found no description of how the Marine Iguanas were kept at the Zoo. Clearly, they did not do well, as was the case with many reptiles until the last thirty years or so.
Moyne also brought a Flightless Cormorant (Phalacrocorax or Nannopterum harrisi) and five Galapagos Doves (Zenaida galapagoensis). David Seth-Smith wrote of their arrival, the first in Britain in the case of the cormorant, in Avicultural Magazine. He provides no further information though on the expedition itself. We can though deduce that Moyne visited the west coast of Isabela (Albemarle) and/or Fernandina (Narborough) since that is the only place in the Galapagos the endemic Flightless Cormorant can be found.
Finally, a few observations in the photograph. I have not been able to identify the publication. It was obviously taken in the public area of the Reptile House—the barriers remain unchanged today. It would appear though that the fronts of some of cages were of wire mesh and not glass. The photograph has an odd appearance and only after looking at it for some time did I realise that Moyne’s hands and arms seem out of place. His right hand is grasping the lizard’s tail but the one shown apparently as the left hand seems to be coming out of thin air. Has there been some heavy retouching, or even the merging of two negatives?
I put some videos I had taken of Galapagos Marine Iguanas (Amblyrhynchus cristatus) on YouTube in 2012. I then had a number of requests from the sort of thick-as-two-short-planks individuals who inhabit that world asking me to tell them where they could buy one.
Export of Galapagos fauna is prohibited by Ecuador and I thought there were none in captivity. Therefore, I was surprised recently to see a Marine Iguana in a video taken by a group of German zoo enthusiasts who were visiting a zoo in Japan in 2016. There have also been reports of some being kept in East Africa.
It would appear that smuggling of Land and Marine Iguanas, if not rife, has been going on. It would be very easy given a small vessel to pick up and ship out Land and Marine Iguanas from many of the islands, just as expedition vessels did in the early decades of the 20th century.
Marine Iguana on Isabella
Marine Iguanas were being traded in the 1960s. A dealer in Florida had some, and small numbers appeared in zoos including Belle Vue in Manchester. Few survived for more than a few weeks, a repeat of attempts to keep them in the 1930s.
However, Brookfield Zoo in Chicago managed to keep four Marine Iguanas for several years, the last dying after being there for over six*. They had been obtained from a dealer in Florida. Re-reading the article by Ray Pawley in the 1966 edition of International Zoo Yearbook on these iguanas I am surprised by this relative success since the conditions in captivity seem very different from those in the wild. They had a small pool with fresh, not sea, water. The humidity was high. However, the key requirements—heat lamps for basking, ultraviolet lamps for vitamin D synthesis—were there. Initially, the iguanas refused all food (as in most zoos up to that time) but Pawley had the idea of putting a Green Iguana into the cage. It settled in and fed immediately, as then did three of the Marine Iguanas on the third day!
Marine iguanas scrape marine algae and any adherent plant and animal life from rocks. Seaweed had been tried in unsuccessful attempts to keep them in captivity. Pawley made up a mixture of chopped vegetables, fruit, meat plus vitamins and minerals. He added some reconstituted kelp. Sea water was sprinkled over this mixture and onto rocks in the cage. This is what the iguanas ate along with with nibbles at plants growing in the cage and some green algae which grew on the rocks. Those who know how to keep Green Iguanas will realise that this mixture, minus the kelp and salt water, would suit just about any mainly herbivorous iguana.
Illustration from Pawley's article in International Zoo Yearbook
The regime was obviously successful since the animals grew and Pawley later reported a great deal of aggression in what must have been the males.
In the same edition of International Zoo Yearbook, Frankfurt Zoo in Germany is listed as also having four Marine Iguanas. I have no information of how they were kept or what became of them.
*I have found wildly differing reports of longevity in the wild; from 5-12 years up to 60.
Pawley R. 1966. Observations on the care and nutrition of a captive group of Marine Iguanas Amblyrhynchus cristatus. International Zoo Yearbook 6, 107-115.
The full list of Pawley’s papers on these animals in in:
Murphy JB. 2015. Studies on Lizards and Tuataras in Zoos and Aquariums. Part I—Introduction, History, Families Iguanidae, Agamidae, Chamaeleonidae, and Infraorder Gekkota. Herpetological Reviews 46, 464-482.
Last week I gave a talk on salt glands to a local group. I remembered that I had not raised a question here that arises from the existence of some very odd animals on one island of the Galapagos.
Everybody knows there are the Marine Iguanas (Amblyrhynchus cristatus) and Land Iguanas (Conolophus sp.) on the Galapagos Islands. Evidence indicates they had a common ancestor about 4.5 million years ago. Watchers of television wildlife programmes cannot fail to have noticed the entirely different lifestyles. Land iguana eat plants and do not venture into the sea. By contrast, Marine Iguanas eat seaweed often foraged at considerable depths.
Over the past forty years it became evident that on one very small island, Plaza Sur, just off the east coast of Santa Cruz (Indefatigable) there were hybrids present between Marine and Land Iguanas (Conolophus subcristatus). These hybrids are sterile as one might expect. There is good evidence that their fathers are male Marine Iguanas, their mothers Land Iguanas. It seems that the breeding seasons of the two species can overlap there. The habitats are very not very far apart either, the thin vegetation where the Land Iguanas bask and feed being only a matter of yards from the rocks on which the Marines bask.
We took video and still photographs of one of these hybrids on Plaza Sur in January 1012. It was lying with Land Iguanas. Local guides say they are not very active and typically have a ‘spaced out’ look like the one below:
Hybrid Marine x Land Iguana, Plaza Sur, 12 January 2012
For comparison: Galapagos Land Iguana, Plaza Sur, 12 January 2012
Also for comparison: Galapagos Marine Iguana, Plaza Sur, 12 January 2012
Nesting burrows of Land Iguanas. Plaza Sur, 12 January 2012
Vegetation on Plaza Sur, 12 January 2012. The marine iguana-like claws of the hybrid iguanas are said to be advantageous in reaching the fruits of the prickly pear. The land iguanas have to wait for them to drop
The question I have had since then is what do the salt glands of these hybrids do? Marine Iguanas have very active salt glands which operate to remove the sodium chloride ingested during feeding. In addition, the concentration of potassium is about ten times higher than in birds which could reflect the high potassium concentration in the plants of their diet. Marine iguanas on land can be seen snorting secretion from the salt glands out of their nostrils, a phenomenon observed by Charles Darwin who did not appreciate its significance to their survival.
Other, species of iguanid lizard have salt glands that can secrete both sodium and potassium. There is evidence that the ratio can be changed by varying the diet. Lizards on a high sodium diet or given a salt load produced a secretion with a more sodium than potassium. As far as I am aware, the Land Iguanas of the Galapagos have not been studied in this respect.
The hybrids seem to live and eat like their Land mothers although I see there are anecdotal reports of their being seen eating seaweed but not entering the water to do so.
So do the hybrid iguanas on Plaza Sur have functional salt glands? How does their size compare with the Marine and the Land? If the salt gland is functional, what are the stimuli for secretion, and does the ratio of sodium:potassium change to reflect changes in the dietary intake?
Possibilities of studying the hybrids to answer these questions are low but the insights into which genes are involved in salt-gland structure and function would be fascinating outcome of this ‘natural experiment’ but biological dead end.
I used this drawing from Bill Dunson's paper in our book on salt glands
I watched Marine Iguanas (Amblyrhynchus cristatus) for hours when we there in 2012: lekking behaviour, males fighting, mating, salt glands in action, feeding on algae, and just sitting around on rocks in large numbers.
Marine Iguanas vary in appearance between the islands and those with an obsession for artificial pigeonholes have created subspecies accordingly. I shall ignore those dated divisions and concentrate on a recent paper* in which mitochondrial and nuclear DNA sequences have been used to investigate the population genetic structure.
This paper has highlighted the tendency towards the splitting into different species—speciation—and the hybridization between lineages that tends to wipe out that tendency. While the split between the Galapagos Land Iguanas and the Marine Iguana was calculated to have occurred 4.5 million years ago, division into genetic lineages in the Marine Iguana was found to be very recent—within the last 50,000 years.
As well as differences between islands, different lineages were even found on one island: San Cristobal or Chatham as it was known in Darwin’s day, and to some of us still is. It is presumed that volcanic events, with their huge lava fields divided the populations at some stage; there was a major eruption 1800-3000 years ago which reduced the population and produced a severe bottleneck in both lineages. What is surprising is that migration and hybridization between these two populations, termed LO (for LoberÃa in the south-west of the island) and PP (for Punta Pitt in the north-east) was uncommon despite there being only 12 km of coastline between them. However, evidence was obtained for hybridization of both LO and PP lineages with animals from other islands rather than the adjacent population. Indeed, migrants were found from Santa Cruz (Indefatigable) and Espaniola (Hood) during the collection of samples. Therefore, introgression of genes from other populations acts to oppose the isolation that would tend towards speciation.
Marine iguana population clusters and phylogenetic relationships. (a) Map of the Galápagos archipelago with major islands colour-coded according to their marine iguana population cluster assignment inferred from structure analysis of 614 individuals genotyped for 12 microsatellite loci (vertical panel in (b)). (b) Species tree cloudogram based on an analysis of 6257 RADSeq-derived SNPs in 33 marine iguanas from across the archipelago, including both San Cristóbal lineages. The graph shows the posterior distribution of consensus trees. Asterisks mark nodes with posterior probability = 1.0 (all other nodes less than 0.9). Specimens were grouped according to population assignment based on structure analysis. From MacLeod et al. 2015
Genetic and morphological differentiation of LO and PP lineages on San Cristóbal Island. LO-SRL and PP-SRPC refer to the original LoberÃa and Punta Pitt localities, photos show adult LO and PP males. (a) Assignment of 454 individuals based on 18 microsatellite loci, after exclusion of inter-island hybrids and migrants. Abbreviations show sampling locations and 1993 marks specimens sampled in that year. (b) Haplotype network of control region sequences (mtDNA) for LO and PP specimens. (c) Map of sampling localities; arrows indicate migrants/hybrids from Santa Cruz (green), Española (orange) and LoberÃa (blue); dagger symbols denote locations of within-island hybrids between PP and LO; triangles denote locations of inter-island hybrids. Population SRECA contains Española migrants/hybrids only. Shaded areas mark lava groups 4–6 aged less than 0.1 Ma [40]. (c) Mean, standard deviation and range of morphological variables differing between LO and PP. ***p < 0.001, **p < 0.01, *p < 0.05; sample sizes above each plot, details and abbreviations in Results and electronic supplementary material. From MacLeod et al. 2015
There are differences in size between lineages, PP for example, being smaller than LO, but I will leave consideration of the significance of that and to what happens during El Niño oscillations, when food in the form of algae is short and the populations of Marine Iguana crash, to another time.
We only visited the south of Cristobal, so saw just those of the LO lineage. The question then, of course, is: which ones did Darwin see when he collected on Chatham (named, like Punta Pitt, after William Pitt the Elder, 1st Earl of Chatham, 1708-1778)? LO, certainly, in the south where there are groups of iguanas around Cerro Brujo, for example, but it is likely that he also saw PP, since some of his landing and collection points were well to the north and within the PP lineage’s range†.
The photographs shows Marine Iguanas from some of the islands we visited:
Española (Hood)
South Plaza
Isabella (Albemarle)
Fernandina (Narborough)
The extent of the lava fields can be seen in this photograph taken on Isabella between from near Darwin Volcano to the south east:
A close-up of the lava on Santiago (James):
…and these are three videos, all taken on a wonderful morning on Fernandina (Narborough):
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*MacLeod A, RodrÃguez A, Vences M, Orazco-terWengel P, GarcÃa C, Reillmich F, Gentile G, Caccone A, Quezada G, Steinfartz S. Hybridization masks speciation in the evolutionary history of the Galapagos marine iguana. Proceedings of the Royal Society. B 282, 20150425.
†Estes G, Grant KT, Grant PR. 2000. Darwin in Galapagos: his footsteps through the archipelago. Notes and Records of the Royal Society of London 54, 343-368.
We were in the Galapagos in January travelling on the motor yacht Cachalote as part of an excellent Naturetrek tour led by Darwin Alvarez. January is an excellent time to visit the Galapagos — the sea is relatively calm, the daytime temperature not too high, the rains are turning the hillsides green and many animals are breeding.
A basking male Marine Iguana on Fernandina
January is the height of the breeding season for Marine Iguanas (Amblyrhynchus cristatus). I had never seen this species alive before despite writing about its salt gland in the 1970s.
After an early morning landing from a panga at Punta Espinoza on Fernandina (Narborough in the old British nomenclature of the islands), we found the Marine Iguanas in the full swing of displaying and mating. On a flattish, large lava bed tens of males were displaying. Females were coming to this site and some were mating. I suddenly realised that what we were seeing was a lek. I could not recall seeing anything about lekking in the guide books and so had to wait until I could do a Google search to see if lekking had been described in this species. Of course, it had — but not until the 1990s, and was the first species of reptile in which this behaviour had been discovered.
Here are some links to accounts of lekking in the Marine Iguana:
I spent some time taking video of Marine Iguanas on Fernandina as well as on the other islands. You can see the area of the lek about half way through this video of mating marine iguanas, as well as shots of the males displaying.
Fierce territorial disputes were also in progress and the next video, taken a few hundred yards from the scene of the first, shows one such dispute:
Incidentally and surprisingly, despite being a major destination for wildlife and general tourism and the excellence of the local guides, there is no really good field guide to the birds and reptiles of the Galapagos.
