On today’s show we learn about the Fiji Crested Iguana, a critically endangered reptile native to roughly 8 islands in the Fijian archipelago in the South Pacific Ocean.
Rough Transcript
Intro 00:05
Welcome to Bad at Goodbyes.
On today’s show we consider the Fiji Crested Iguana.
Species Information 02:05
The Fiji Crested Iguana is a critically endangered reptile native to roughly 8 islands in the Fijian archipelago in the South Pacific Ocean. Its scientific name is Brachylophus vitiensis.
Appearance
The Fiji Crested Iguana is a large, stocky long-tailed lizard that can reach lengths of up to 30 inches. That’s mostly tail; roughly ten inches of body and 20 inches of tail. They weigh roughly three-quarters of a pound.
Their scales are a bright emerald green, with three narrow, cream-to-white bands that run vertically along their sides. The scales are small and granular, giving their skin a rough, kind of pixelated texture.
As suggested by their name, they have a spiny crest that extends along their back, from the nape of the neck to the base of the tail. This is a dense row of elongated, pointy, modified scales that can grow up to half an inch in length. This crest is thought to be a defensive adaptation. Though not as formidable as say the spines of a porcupine, the iguana’s crest may make it harder for predators to grip it and consume it. The crest is also a visual deterrent, making the iguana seem larger and more threatening to potential predators.
The Fiji Crested Iguana is quadrupedal, meaning it moves on all four limbs. They have really long slender toes, five per foot, each ending in sharp claws.
They have a slightly elongated snout, with two large bright yellow nostrils at the tip. Their eyes are also large, with a golden or reddish iris and a deep black pupil. Near the hinge of the jaw on both sides of the head is an oval-shaped tympanum, this is the external ear opening, a thin, unscaled, skin-like membrane, which passes soundwaves, allowing them to hear.
A fleshy dewlap hangs beneath the chin, a dewlap is a piece of elastic loose skin that can be used in displays of courtship or aggression. Specialized musculature allows the iguana to extend or fan out the dewlap to make themselves appear larger and more intimidating.
The Fiji Crested Iguana also can change its scale color from green to nearly black when threatened. This adaptation allows the iguana to blend in with its surroundings, to startle potential predators, and to menace potential rivals. The iguana synthesizes additional melanin, the same chemical compound found in human hair and skin, and so more melanin results in darker scale pigmentation.
Fijian iguanas, including the Fiji Crested Iguana, are the most geographically isolated iguanas in the world, with their closest relatives found in South America.
DNA and fossil evidence suggests that the Fijian iguanas diverged from the Americas branch of the iguana family roughly 35 million years ago. So, how did they end up in the South Pacific?
One proposed hypothesis is that modern Fijian Iguanas descended from a widespread, but now extinct lineage, a shared ancestor with the Iguanas of the Americas from perhaps 40-60 million years ago. However, no evidence of this lineage, living or in the fossil record has been found.
And so the more widely accepted hypothesis is that they rafted. Making a roughly 7 thousand mile transoceanic journey from the Americas to the South Pacific, on driftwood, or on buoyant tangled plant masses, imagine vegetation uprooted by a storm floating out on the sea. And of course we’re not talking about a single iguana, a single iguana cannot reproduce, and even a breeding pair gets genetically messy quickly, so this is likely a small population making this epic trip.
I do want to stress that this was not intentional, this was not a migration, we should not imagine iguana seeking a new food source by adventuring on driftwood. It is surely accident or calamity that finds this population swept to sea and then it is mostly wild good luck that they survive the trip and eventually find land in Fiji. The Pacific is big and there is not much land, fresh water or food between say Peru and Fiji.
So luck plays a role: And there are a few more tangible factors on their side. First: the South Equatorial Current. This is a broad westward-flowing current across the Pacific, that could have provided potential propulsion for the rafting iguana to reach Fiji.
Other promising considerations are physiology. Iguana have a relatively low metabolic rate and can survive for extended periods without food or fresh water. They have a higher tolerance for saltwater exposure than many terrestrial animals. They are relatively long lived, with lifespans up to 15 years. And they have very long reproductive cycles, only breeding and birthing once every two years.
So I did a little back-of-the-envelope math on this. The Pacific South Equatorial Current flows, at the surface, on average roughly half a mile per hour. This is a 7000 mile journey, so under like ideal conditions, with a steady current flow and no drifting or meandering, we’re looking at about one year and 7 months to make the trip.
Please note: that is a totally speculative number based on rough estimate and presumption. I’m just wanting to get a picture of this journey and it obviously is a really big trip, but also feels plausible.
One last point here, this really only has to happen once. A small population makes it to a super lush island with no predators and it thrives and evolves. And there are 10s of millions of years over which this might have happened.
So however improbable rafting iguanas sounds at first, it is our leading hypothesis, and when we talk it through, it does feel plausible.
Fiji Crested Iguana are diurnal and arboreal. Meaning they are active during the day and spend most of their time in the forest canopy. Their long toes, claws and tail, are adapted for climbing and they move through the treetops foraging for food and basking in sunny patches to regulate their body temperature, as they are cold-blood. They even sleep in the trees.
They are herbivorous, eat leaves, buds, flowers, and fruit from a range of forest plants including the Cevua tree, the Karanja tree, passionfruit, and show a preference for the sweet hibiscus flowers of the Vau tree.
They are primarily solitary and can be territorial, particularly during the breeding season, defending their home range from potential rivals. Using visual displays, such as head bobs, dewlap extensions and scale color change, as well as pheromonal chemical signals used to mark territory. These communications establish dominance over other Fiji Crested Iguana and are used to attract mates.
Breeding season peaks in March and April. Copulation occurs in the trees and then the female make a rare trek to ground for egg laying. Using her clawed forelimbs, she digs a burrow in the forest floor, just slight larger than the size of her body, into which she lays a clutch of 2-4 eggs. She then fills in the nest with loose soil, closing off the entrance, and packing dirt in with her forelimbs and snout. She then camouflages the nest by kicking debris, stones and leaf litter over top. A 2009 study reports that “Completed nest sites were virtually indistinguishable from the surrounding forest floor.”
The female returns to the treetop and there have been no observations of defence of the nest and or of parental care for the young. The eggs will then incubate underground for up to 9 months, which is quite long, hatching in October, November, December.
Hatchlings are precocial, meaning they are well-developed and independent from birth, emerging from the eggs able to walk, climb, forage, and avoid predators. They’re like miniature versions of the adults, measuring roughly 5 inches in length. They grow slowly, not reaching reproductive maturity until 3 to 5 years of age. And can live up to 15 years.
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In the dream to drift the seas unwitting, in the dream to be truly lost, all horizons unfamiliar, in the dream a feral despairing, a long aching thirst, a monotony of blue and then, oh and then, green land, a new home,
In the dream
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The Fiji Crested Iguana is native to the Fiji Islands in the South Pacific Ocean specifically roughly 8 of the western islands of the archipelago, including Yadua Taba, Macuata, and Malolo Levu.
The islands formed where the Pacific Plate subducts beneath the Australian Plate. Subduction occurs where two tectonic plates meet and one plate slides beneath the other, pressed downward into the Earth’s mantle, the layer beneath the crust. As the subducting plate descends into the mantle increasing temperature and pressure buildup leads to magma release causing volcanic eruptions. And over time, these volcanic eruptions build up layers of cooled lava, eventually forming the islands we see today.
The Fijian islands evidence this volcanic history, marked by rugged mountains, craters of both dormant and active volcanoes, hot springs and occasional earthquakes.
We find the Fiji Crested Iguana in the trees of the island’s dry forests. These are deciduous forests, unlike the evergreen rainforests found in other parts of the archipelago, many of the trees in the dry forest shed their leaves during the dry season, which typically lasts from May to October. Temps in this cooler dry season average in the mid 70s°f, while temps in the wet season that’s Nov-Apr, average in the 80s°F. The region receives roughly 70 inches of rainfall per year, of course most of it falling during the wet season. The contrast is striking; for comparison, March can see up to 15 inches of rainfall, while July may see less than 1 inch.
The Fiji Crested Iguana shares its island home with:
Orange Dove, Passionfruit, Fiji Stick Insect, Orchid, Dakua, Pacific Swallow, Vau, Kauloa, Red-vented Bulbul, Fiji Banded Iguana, Sandalwood, Karanja, Red-Throated Lorikeet, Coconut Crab, Lime Berry, Fijian Monkey-Faced Bat, Cevua, Pacific Boa, Green Turtle, Collared Lory, Yaqata, Mourning Gecko, Fiji land snail, Guava, Fijian swallowtail, and many many more.
The Fiji Crested Iguana population is threatened by deforestation resulting in habitat loss and degradation. Significant patches of healthy dry forest are now rare in Fiji, following decades of burning, clearing for agriculture, overgrazing by human introduced goats, the spread of invasive plants, and by the expansion of infrastructure and tourism development.
Additionally human-introduced predators such as feral cats and rats prey on the iguana, especially juveniles and eggs. Which is particularly damaging for a species like the Fiji Crested Iguana who has long reproduction cycles.
Human induced Climate change is an emerging threat. Rising sea levels and increased frequency of extreme weather events, such as cyclones, can inundate nesting sites and damage critical habitat. Changes in temperature and rainfall patterns can also affect food availability and disrupt the balance of the dry forest ecosystem.
Fortunately there have been substantial conservation efforts to protect the Fiji Crested Iguana. With some marked successes. The National Trust of Fiji has established the entirety of Yadua Taba island as a protected reserve, including the eradication of invasive goat species, and the reintroduction of native plants to help restore the iguana’s habitat. The island is off-limits to the public, and visits require permitting, granted strictly for scientific and conservation use.
A partnership initiated between a private resort owner and the Fijian government on the island Malolo Levu is also exploring dry-forest restoration, including an experimental nursery dedicated to cultivating saplings of native species intend to reforest sections of the island, creating natural, self-propagating iguana habitat. That program is also removing non-native predators like feral cats, dogs, and rats.
A captive breeding and reintroduction program has had success hatching iguana eggs in captivity and researchers report increased sightings of iguanas in their natural habitat.
Nevertheless the Fiji Crested Iguana has been considered critically endangered on the IUCN Red List since 1996 and their population is currently in decline.
Our most recent counts estimate less than 14000 Fiji Crested Iguana remain in the wild.
Citations 27:59
Australian Journal of Zoology v. 55, 341-350. Morrison Clare, Osborne Tamara, Harlow Peter S., Thomas Nunia, Biciloa Pita, Niukula Jone (2008) “Diet and habitat preferences of the Fijian crested iguana (Brachylophus vitiensis) on Yadua Taba, Fiji: implications for conservation”. – https://doi.org/10.1071/ZO07062
Ecology and Evolution vol. 11 no.9: 4731-4743. 26 Mar. 2021. Eliades, Samuel J et al. “Gut microbial ecology of the Critically Endangered Fijian crested iguana (Brachylophus vitiensis): Effects of captivity status and host reintroduction on endogenous microbiomes.” – https://doi.org/10.1002/ece3.7373
Iguana, v. 11 no.4, 198-205. Harlow, P. S. (2004). “Lost in the South Pacific: The Fijian Iguanas (Genus Brachylophus).” – https://journals.ku.edu/iguana/article/view/17149
Harlow, P., Fisher, R. & Grant, T. 2012. Brachylophus vitiensis. The IUCN Red List of Threatened Species 2012: e.T2965A2791620. https://dx.doi.org/10.2305/IUCN.UK.2012.RLTS.T2965A2791620.en
IUCN Fijian crested iguana. Brachylophus vitiensis : species recovery plan, 2008-2012. Harlow, Peter S – https://portals.iucn.org/library/node/46149
Journal of Herpetology v.15, no. 3 (1981): 255–73. John R. H. Gibbons. “The Biogeography of Brachylophus (Iguanidae) Including the Description of a New Species, B. Vitiensis, from Fiji.” – https://doi.org/10.2307/1563429
National Trust of Fiji Islands – https://nationaltrust.org.fj/iguana/
Oryx. v 41. Harlow, Peter & Fisher, Martin & Tuiwawa, Marika & Biciloa, Pita & Palmeirim, Jorge & Mersai, Charlene & Naidu, Shivanjani & Naikatini, Alivereti & Thaman, Baravi & Niukula, Jone & Strand, Erica. (2007). “The decline of the endemic Fijian crested iguana Brachylophus vitiensis in the Yasawa and Mamanuca archipelagos, western Fiji.” – http://dx.doi.org/10.1017/S0030605307001639
Pacific Conservation Biology. v. 15. pg.135-147. Morrison, Suzanne & Harlow, Peter & Keogh, J.. (2009). “Nesting ecology of the critically endangered Fijian Crested Iguana Brachylophus vitiensis in a Pacific tropical dry forest.” – http://dx.doi.org/10.1071/PC090135
Pacific Science v.63 no. 2, 223-242, (1 April 2009). Clare Morrison, Gunnar Keppel, Nunia Thomas, Isaac Rounds, and Peter S. Harlow “Critically Endangered Fijian Crested Iguana (Brachylophus vitiensis) Shows Habitat Preference for Globally Threatened Tropical Dry Forest,” – https://doi.org/10.2984/049.063.0205
PloS one. 8. E73127. Morrison, Suzanne & Biciloa, Pita & Harlow, Peter & Keogh, J.. (2013).” Spatial Ecology of the Critically Endangered Fijian Crested Iguana, Brachylophus vitiensis, in an Extremely Dense Population: Implications for Conservation.” – https://doi.org/10.1371/journal.pone.0073127
Proceedings of the international conference on island invasives 2017: Island invasives : scaling up to meet the challenge. ed: Veitch, C.R. “Community-based conservation and recovery of native species on Monuriki Island, Fiji.” (2019). Fisher, Robert N., Jone Niukula, Peter S. Harlow, Sia Rasalato, Ramesh Chand, Baravi Stewart Helu Thaman, Elenoa Seniloli, Joeli Vadada, Steve Cranwell, J. Jed Brown, Kim Lovich and Nunia Thomas-Moko. – https://doi.org/10.2305/IUCN.CH.2019.SSC-OP.62.EN
Reptiles & Amphibians, v. 29 no.1, 243-249. Anstey, S. (2022). “Saving the Fijian Crested Iguana (Brachylophus vitiensis)”. – https://doi.org/10.17161/randa.v29i1.16749
Wikipedia – https://en.wikipedia.org/wiki/Fiji_crested_iguana
For more information about Fiji Crested Iguana conservation please see National Trust of Fiji Islands – https://nationaltrust.org.fj/iguana/
Music 29:52
Pledge 36:21
I honor the lifeforce of the Fiji Crested Iguana. I will commit its name to my record. I am grateful to have shared time on our planet with this being. I lament the ways in which I and my species have harmed and diminished this species. I grieve.
And so, in the name of the Fiji Crested Iguana I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of plant and animal kin and their habitat, by individuals, corporations, and governments.
I forever pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.
