---
title: "What the sources say about the Marine Iguana | AnimalTracks.wiki"
description: "42 claims from the Marine Iguana profile, each beside the words of the source that backs it."
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# What the sources say about the Marine Iguana (*Amblyrhynchus cristatus*)

> 42 claims from the Marine Iguana profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Marine Iguana](https://animaltracks.wiki/animals/marine-iguana/)

## Marine iguana. Galapagos Conservation Trust.

https://galapagosconservation.org.uk/species/marine-iguana/

| The page says | The source says |
| :--- | :--- |
| On average they measure about 0.7 meters and weigh 1.5 kilograms | Average size: 0.7 metres ... Average weight: 1.5 kilograms |
| they typically live 5 to 12 years | Average lifespan: 5 - 12 years |
| using sharp claws to hold the rock | use their powerful claws to grip on to rocks in strong currents to feed |
| and it comes loaded with salt | Due to the high concentration of salt in their diet |
| filter it out of the blood, and the iguana sneezes the excess away, often leaving salt crystals on its snout | marine iguanas filter their blood at the nose and sneeze out the excess salt, often forming salt crystals on the snout |
| Entering the water also slows its heartbeat to half its normal pace, saving energy so it can feed for as long as possible. | Upon entering the water, their heartbeat slows to half its normal pace in order to conserve energy and allow them to feed for as long as possible |
| Skeletal shrinkage of up to 20% during El Niño food shortages, and nasal glands that expel excess salt | shrinking their skeleton by up to 20% to reduce their need for food |
| To cope with El Niño, marine iguanas can shrink their own skeleton by up to 20 percent, cutting how much food they need. | adaptations to deal with the effects of the El Niño climate phenomenon, including shrinking their skeleton by up to 20% to reduce their need for food |
| they have cut marine iguana populations by up to 85 percent | El Niño periodically decreases the iguana population (by up to 85%) |
| Their diet is so salty that they filter the salt from their blood at the nose and sneeze it out, often leaving crystals on the snout. | Due to the high concentration of salt in their diet, marine iguanas filter their blood at the nose and sneeze out the excess salt, often forming salt crystals on the snout |
| During El Niño its skeleton can shrink by as much as a fifth, lowering its need for food | adaptations to deal with the effects of the El Niño climate phenomenon, including shrinking their skeleton by up to 20% to reduce their need for food (note: "a fifth" is 20% ("up to 20%")) |
| weightKg: 1.5 | Average weight: 1.5 kilograms (note: battleStats (settle #880)) |
| Entering the water slows its heartbeat to half its normal pace, saving energy so it can feed for longer | Upon entering the water, their heartbeat slows to half its normal pace in order to conserve energy and allow them to feed for as long as possible (note: vibe.reason (settle #880)) |

## Marine Iguana. Oceana.

https://oceana.org/marine-life/marine-iguana/

| The page says | The source says |
| :--- | :--- |
| The only lizard in the world that forages in the ocean, grazing algae underwater and sneezing out the salt. | The marine iguana is the only lizard in the world that forages in the ocean |
| The Only Lizard That Forages at Sea | The marine iguana is the only lizard in the world that forages in the ocean |
| the marine iguana (Amblyrhynchus cristatus) is the only lizard on Earth that forages in the ocean | The marine iguana is the only lizard in the world that forages in the ocean |
| Larger iguanas dive up to 30 meters (98 feet) to reach algae beds beneath the waves, using sharp claws to hold the rock and a flattened tail to swim, while smaller animals stay close to shore and graze algae exposed at low tide. | smaller individuals grazing on exposed algae between tides while larger iguanas dive up to 30 meters (98 feet) deep to reach algal beds beneath the waves |
| and a flattened tail to swim | sharp claws benefit their ability to graze underwater, while their flattened tail helps them swim through the waves |
| Marine algae grazed from submerged volcanic rock, reached by diving or exposed at low tide | smaller individuals grazing on exposed algae between tides while larger iguanas dive up to 30 meters (98 feet) deep to reach algal beds beneath the waves |
| Specialized glands in the nose filter it out of the blood | the ability to excrete salt consumed from seawater through specialized glands in their noses |
| El Niño events warm the ocean and reduce algal growth, which can bring food shortages and mass die-offs | El Niño events, which warm ocean waters and reduce algal growth, can lead to food shortages and mass die-offs |
| Even so, larger iguanas dive as deep as 30 meters (98 feet) for algae, while smaller ones graze what low tide leaves exposed. | smaller individuals grazing on exposed algae between tides while larger iguanas dive up to 30 meters (98 feet) deep to reach algal beds beneath the waves (note: "as deep as" keeps "up to") |

## Amblyrhynchus cristatus (Marine Iguana). Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Amblyrhynchus_cristatus/

| The page says | The source says |
| :--- | :--- |
| Marine algae is almost the only thing on the menu | The marine iguana feed almost exclusively on marine algae |
| nasal glands that expel excess salt | excretes concentrated salt crystals from a nasal gland (note: stats.superpower) |
| Rocky shorelines, low rock ledges and intertidal flats of the volcanic Galápagos Islands | found on the volcanic islands of the Galapagos. Many of the islands have steep rock cliffs, low rock ledges and intertidal flats (note: this is stats.habitat; "rocky shorelines" paraphrases "steep rock cliffs" and GCT's "coastal regions") |

## Wikelski & Trillmich (1997). BODY SIZE AND SEXUAL SIZE DIMORPHISM IN MARINE IGUANAS FLUCTUATE AS A RESULT OF OPPOSING NATURAL AND SEXUAL SELECTION: AN ISLAND COMPARISON. Evolution.

https://doi.org/10.1111/j.1558-5646.1997.tb03673.x

| The page says | The source says |
| :--- | :--- |
| Size swings wildly between islands. | populations in the Galápagos exhibit 10-fold differences in body mass between island populations |
| A study comparing two of them found the heaviest males on Genovesa weighed about 900 grams, while those on Santa Fé reached 3,500 grams | two island populations (max. male mass 900 g in Genovesa, 3500 g in Santa Fé) (note: "heaviest" paraphrases "max. male mass"; scoped to the paper's two-island comparison) |
| Males are roughly twice as heavy as females. | males being about twice as heavy as females |

## Romero & Wikelski (2010). Stress physiology as a predictor of survival in Galapagos marine iguanas. Proceedings of the Royal Society B: Biological Sciences.

https://doi.org/10.1098/rspb.2010.0678

| The page says | The source says |
| :--- | :--- |
| One study measured 98 adult males, then waited: months later a weak El Niño struck and 23 of them died. | we captured 98 adult male marine iguanas ... Several months after collecting initial measurements, weak El Niño conditions affected the Galápagos and 23 iguanas died |
| The dead and the survivors had not differed in how strongly they reacted to stress. | We found no prior differences between dead and alive iguanas in baseline corticosterone concentrations, responses to acute stressors, nor in capacity to respond |
| The dead had been worse at switching the stress hormone back off, which suggests that ending a stress response quickly helps an iguana survive starvation. | The dead iguanas were typified by a reduced efficacy of negative feedback (i.e. poorer post-stress suppression of corticosterone release) compared with surviving iguanas ... These data suggest that a greater ability to terminate a stress response conferred a survival advantage during starvation (note: "quickly" is a paraphrase of "greater ability to terminate"; hedge "suggest" kept) |

## Trillmich (1983). The Mating System of the Marine Iguana (Amblyrhynchus cristatus). Zeitschrift für Tierpsychologie.

https://doi.org/10.1111/j.1439-0310.1983.tb00084.x

| The page says | The source says |
| :--- | :--- |
| On Caamaño islet, where a study followed one breeding colony, females were ready to mate during only 24 days in January. | was studied on Caamaño islet ... The mating readiness of females was well synchronized to only 24 days in Jan. |
| Territorial males cut back their foraging and fasted for a median of 12 days that month, losing up to 26 percent of their body weight. | males shortened their foraging time and even fasted for some time in Jan. (median fast duration 12 days). They lost up to 26% body weight during this period |

## Vitousek et al. (2007). Heterospecific alarm call recognition in a non-vocal reptile. Biology Letters.

https://doi.org/10.1098/rsbl.2007.0443

| The page says | The source says |
| :--- | :--- |
| Marine iguanas have no voice of their own, yet they can eavesdrop on the alarm call of the Galápagos mockingbird and respond with anti-predator behavior. | a non-vocal reptile, the Galápagos marine iguana ( Amblyrhynchus cristatus ), can eavesdrop on the alarm call of the Galápagos mockingbird ( Nesomimus parvulus ) and respond with anti-predator behaviour |
| Before a 2007 study showed this, the trick had been described only in animals that make calls themselves. | The ability to recognize and respond to the alarm calls of heterospecifics has previously been described only in species with vocal communication (note: 2007 is the study's publication year (reference heterospecific-2007, Biology Letters 2007); "before" paraphrases "previously") |
| Not in their own voices: they are non-vocal. Instead they tune in to a bird, and the Galápagos mockingbird's warning call puts them on guard against predators. | a non-vocal reptile, the Galápagos marine iguana ( Amblyrhynchus cristatus ), can eavesdrop on the alarm call of the Galápagos mockingbird ( Nesomimus parvulus ) and respond with anti-predator behaviour |

## Thompson (2015). “Only the Amblyrhynchus”: Maria Graham’s Scientific Editing of Voyage of HMS Blonde (1826/27). Journal of Literature and Science.

https://doi.org/10.12929/jls.08.1.04

| The page says | The source says |
| :--- | :--- |
| HMS Blonde called at the islands | the Blonde had visited the Galapagos Islands |
| on its 1824-25 voyage | the 1824-25 voyage of HMS Blonde (note: the paper dates the voyage 1824-25 and says the Blonde visited the Galapagos; it gives no year for the Galapagos call, so the page gives none) |
| the published account of the trip, edited by Maria Graham | Maria Graham, who in 1826 was commissioned by the publisher John Murray to produce an account of a recent naval expedition (note: the quoted words are in the published narrative Graham produced; the paper thinks she likely coined the phrase from Dampier's journal (note 9 allows the chaplain Bloxam as source), so the page attributes it to the published account only) |
| described the iguanas sitting on the black lava rocks "like so many imps of darkness." | sat on the black lava rocks like so many imps of darkness (note: the quoted words are in the published narrative Graham produced; the paper thinks she likely coined the phrase from Dampier's journal (note 9 allows the chaplain Bloxam as source), so the page attributes it to the published account only) |

## MacLeod, Nelson & Grant (2020). Amblyrhynchus cristatus. The IUCN Red List of Threatened Species 2020: e.T1086A177552193.

https://doi.org/10.2305/iucn.uk.2020-2.rlts.t1086a177552193.en

| The page says | The source says |
| :--- | :--- |
| Vulnerable | IUCN Red List category: Vulnerable (VU). (note: category read through GBIF's copy of the Red List, checked against IUCN taxon 1086; this is stats.conservationStatus) |

## Lewbart et al. (2015). Blood gases, biochemistry and haematology of Galápagos marine iguanas (Amblyrhynchus cristatus). Conservation Physiology.

https://doi.org/10.1093/conphys/cov034

| The page says | The source says |
| :--- | :--- |
| On San Cristóbal, 35 iguanas measured from nose to tail tip ran 72.5 to 121 centimeters | A total of 35 marine iguanas (24 males, four females and seven immature) were sampled from three locations on San Cristobal Island. The mean SVL for the entire group was 40.5 cm (28.5–51.0 cm) and the mean TL (tip of nose to tip of tail) was 98.1 cm (72.5–121.0 cm) (note: replaces GCT's 'Maximum size: 1.5 metres', which no primary total-length measure supports (settle #940)) |