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Amblyrhynchus cristatus. The IUCN Red List of Threatened Species

Authors:
The IUCN Red List of Threatened Species™
ISSN 2307-8235 (online)
IUCN 2020: T1086A177552193
Scope(s): Global
Language: English
Amblyrhynchus cristatus, Marine Iguana
Errata version
Assessment by: MacLeod, A., Nelson, K.N. & Grant, T.D.
View on www.iucnredlist.org
Citation: MacLeod, A., Nelson, K.N. & Grant, T.D. 2020. Amblyrhynchus cristatus (errata version
published in 2020). The IUCN Red List of Threatened Species 2020: e.T1086A177552193.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T1086A177552193.en
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THE IUCN RED LIST OF THREATENED SPECIES™
Taxonomy
Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Iguanidae
Scientific Name:ÊÊAmblyrhynchus cristatus Bell, 1825
Infra-specific Taxa Assessed:
Amblyrhynchus cristatus ssp. albemarlensis
Amblyrhynchus cristatus ssp. cristatus
Amblyrhynchus cristatus ssp. cristatus
Amblyrhynchus cristatus ssp. godzilla
Amblyrhynchus cristatus ssp. hassi
Amblyrhynchus cristatus ssp. hayampi
Amblyrhynchus cristatus ssp. jeffreysi
Amblyrhynchus cristatus ssp. mertensi
Amblyrhynchus cristatus ssp. mertensi
Amblyrhynchus cristatus ssp. nanus
Amblyrhynchus cristatus ssp. sielmanni
Amblyrhynchus cristatus ssp. trillmichi
Amblyrhynchus cristatus ssp. venustissimus
Amblyrhynchus cristatus ssp. venustissimus
Amblyrhynchus cristatus ssp. wikelskii
Common Name(s):
• English: Marine Iguana, Galápagos Marine Iguana, Sea Iguana
• French: Amblyrhynche à crête, Iguane marin
• Spanish; Castilian: Iguana Marina
• German: Meerechse
Taxonomic Source(s):
Iguana Taxonomy Working Group (ITWG). 2016. A checklist of the iguanas of the world (Iguanidae;
Iguaninae). In: J.B. Iverson, T.D. Grant, C.R. Knapp and S.A. Pasachnik (eds), Iguanas: Biology,
Systematics, and Conservation, pp. 4–46. Herpetological Conservation and Biology 11(Monograph 6).
Taxonomic Notes:
The Marine Iguana (genus Amblyrhynchus) is a single species, with 11 subspecies after taxonomic
revision by Miralles et al. (2017).
Assessment Information
Red List Category & Criteria: Vulnerable A2abce+4abce ver 3.1
Year Published: 2020
Date Assessed: December 1, 2019
Justification:
Marine Iguanas occur on the large islands of Española, Fernandina, Floreana, Genovesa, Isabela,
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
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Marchena, Pinta, San Cristobál, Santa Cruz, Santa Fé, and Santiago, the mid-sized islands of Baltra,
Bartolomé, Pinzón, Plaza Norte, Plaza Sur, Rábida, and Seymour Norte, smaller key populations on
Darwin, Roca Redonda, and Wolf, as well as many satellite islets of the Galápagos Archipelago, Ecuador.
The estimated extent of occurrence is 56,647 km2 by minimum convex polygon and the area of
occupancy is estimated at 42,155 km2 using a 2x2 km grid overlay within a coastal buffer 2 km from the
shore. The population size is poorly known and crudely estimated as low as 33,000 total iguanas after a
strong El Niño famine and as many as 350,000 after several years of La Niña abundant food conditions,
with fewer than 210,000 mature individuals. Current taxonomy describes eleven subspecies. Only one
subspecies has a genetically resilient effective population size, and only one more is close to the
threshold to be considered healthy; the remaining are critically low to moderate. Overall population
trend is unknown, but is subject to extreme fluctuations and reductions during El Niño events (10–90%
mortality), which are predicted to intensify in the future with ongoing climate change.
Marine Iguana populations have been reduced by invasive alien predators such as feral cats, rats, and
free-roaming pigs and dogs on five of the 13 main islands (ca 30% of the total population). These
iguanas are threatened by a region-wide increase in human population and visitation that has multiplied
the impacts from stress, marine pollution including oil and diesel spills, habitat degradation, and chance
of further invasive species introductions and emergent diseases. Land-based tourist presence and
intensity has been shown to have a significant overall negative effect on iguana health. Overall
population trends are difficult to estimate without comprehensive population size monitoring data,
however, the multitude of known anthropogenic threats found across the archipelago are sufficient to
support an estimate of an overall population reduction of at least 30% over the last three generations.
Without significant invasive species control and enhanced protection from marine pollution, declines
are projected to continue in the near future, exacerbated by increasingly frequent and severe El Niño
events and human impacts that affect all populations. We estimate that the per cent reduction over the
past two generations and one generation into the future (ca 18–24 years) will also be at least 30%. This
species qualifies for listing as Vulnerable.
Previously Published Red List Assessments
2004 – Vulnerable (VU)
https://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T1086A3222951.en
1996 – Vulnerable (VU)
1994 – Rare (R)
1990 – Rare (R)
1988 – Rare (R)
1986 – Rare (R)
Geographic Range
Range Description:
The Marine Iguana occurs on the large islands of Española, Fernandina, Floreana, Genovesa, Isabela,
Marchena, Pinta, San Cristobál, Santa Cruz, Santa Fé, and Santiago, the mid-sized islands of Baltra,
Bartolomé, Pinzón, Plaza Norte, Plaza Sur, Rábida, and Seymour Norte, smaller key populations on
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T1086A177552193.en
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Darwin, Roca Redonda, and Wolf, as well as many satellite islets of the Galápagos Archipelago, Ecuador.
This species has an extent of occurrence of 56,647 km2 by minimum convex polygon enclosing all
subpopulations, that includes the far distant small islands of Darwin and Wolf. A minimum convex
polygon enclosing just the central islands (without Darwin and Wolf) of occurrence is 42,155 km2.
Marine Iguanas are found within 2 km of the coast with a total area of occupancy of 4,368 km2, using a
2x2 km grid overlay in this coastal zone. They are found near (< 200 m asl) and below sea level at depths
up to 30 m (large adult males).
Country Occurrence:
Native, Extant (resident): Ecuador (Galápagos)
FAO Marine Fishing Areas:
Native: Pacific - southeast
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
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Distribution Map
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T1086A177552193.en
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Population
Only very rough estimates of population size are available for the entire population of Marine Iguanas.
They are noted to be as low as 33,000 total individuals after a strong El Niño famine and as many as
350,000 after several years of La Niña abundant food conditions (Wikelski and Nelson 2004). Little is
known regarding current mature adult numbers, but it is estimated to be under 210,000 based on
calculations indicating that 60% of the maximum total population are adults (Laurie 1983, Laurie and
Brown 1990a, MacLeod et al. 2016).
Average generation length is five years for females and 12 years for males (6–8 years is used for
calculations). Approximately 20–30% of the total population (ca 10,000–73,000) is estimated to be
declining due to the continual impacts of invasive alien predators. Sharp declines relating to these
threats have been reported since the early 1980s (Laurie 1983, Jacome 1989, Cayot et al. 1994, Wikelski
and Nelson 2004, MacLeod and Steinfartz 2016); covering a period of well over three generations. A
severe absence of younger iguanas in some colonies has been observed, most notably on Floreana,
Isabela, Santa Cruz, and San Cristóbal (Laurie 1983).
Recent genetic analysis indicates that the subpopulations (subspecies) show a variable effective
population size, from critically low (A. c. godzilla) to healthy (A. c. cristatus) (range: 37–2,388; MacLeod
and Steinfartz 2016). Subspecies with very low values may show consequences of inbreeding and have
reduced ability to adapt to rapidly changing environmental conditions (Ne > 1,000 minimum; Frankham
et al. 2014).
Populations undergo extreme fluctuations by cyclic, but unpredictably recurring, famine (El Niño) and
feast (La Niña) events. El Niño events dramatically reduce the abundance, diversity, and nutritional value
of available marine algae, as the iguanas are unable to digest the algae that grows during these periods
(Trillmich and Trillmich 1986). Population declines are strongly density-dependent: the higher the
population density, the higher the mortalities during El Niños (from 10–90%). Population recovery after
El Niños can be rapid if food resources are available again, as individuals grow faster, reproduce more
frequently and lay more eggs (Laurie and Brown 1990a).
The lack of population size monitoring data presents a challenge when assessing the overall population
trajectory. However, surveys in the 1980s noted that the species was in danger of extirpation on several
islands (Laurie 1983) and subsequent work noted a further decline (Cayot et al. 1994). In 2002, the
number of iguanas on San Cristóbal, Santa Cruz, and Santiago was noted to be significantly less than
expected (Snell and Márquez 2002). Indeed, the multitude of known and predicted future
anthropogenic threats found across the archipelago are sufficient to support a finding of an overall
population reduction of at least 30% over the last four decades. Without significant invasive species
control and enhanced protection from marine pollution, declines are projected to increase in the future,
exacerbated by increasingly frequent and severe El Niño events that affect all populations.
Current Population Trend:ÊÊDecreasing
Habitat and Ecology (see Appendix for additional information)
Marine Iguanas are the only lizard species that forage in the ocean. Adults and juveniles occur on rocky
coasts and intertidal zones. Adult females can be found nesting up to 2 km inland and adult males can
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
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be found foraging in marine waters, up to depths of 30 m. They feed almost exclusively on marine algae,
primarily three red genera (Centroceras, Gelidium, Pterocladia; Rubenstein and Wikelski 2003) and the
green algal genus Ulva when exposed during low tides (Shepherd and Hawkes 2005). The majority of
iguanas graze intertidally, though the largest iguanas of each colony also dive beneath the sea surface to
forage on offshore algal beds (30 m offshore, 2–30 m depth; Buttemer and Dawson 1993, Wikelski and
Trillmich 1994). Some iguana populations have been known to supplement their algal diet with highly
salty land plants, primarily Saltwort (Batis maritima), but also other coastal succulents such as Sesuvium
portulacastrum (Wikelski and Wrege 2000).
Marine Iguanas exhibit high morphological diversity, including substantial body size and shape variation
among populations and sexes (Chiari et al. 2016). Males are larger, with different head morphology than
females and more pronounced spines on the head and along the back. Average body size (snout-to-vent
length) is 260 mm (range 120–490 mm; Miralles et al. 2017). Adult males weigh approximately 70%
more than adult females (Laurie and Brown 1990a). Differences in maximum body size across islands is
likely due to variability in algal productivity and sea surface temperature between islands (Wikelski and
Trillmich 1997, Wikelski and Romero 2003, Wikelski 2005).
Reproduction occurs once a year during a month-long mating season, coinciding with the highest
abundance and best nutritional quality of food (Rubenstein and Wikelski 2003). Nutrient-rich upwellings
from the Humboldt and Cromwell currents affect all islands differently, so mating occurs at different
times across the archipelago, varying somewhat from year to year. During this time males tend to
become more colourful.
Marine Iguanas are the only lizard known to use a lek mating system, in which dominant males defend
small territories (without resources beyond themselves) from other males. Male mating success is highly
skewed to a few individuals and depends on body size, condition, and head-bob courtship behaviour. A
single territorial male may be responsible for 35% of copulations on a lek (Trillmich 1983; Wikelski et al.
1996, 2001). Non-territorial males roam the periphery and try to force copulations with females,
although they are rarely successful (Wikelski and Bäurle 1996). “Sneaker” males (physically small and
resembling females) occupy the territories and also try to force copulations with females, which is also
almost never successful.
Around four weeks after mating, females seek out and defend suitable sandy areas for digging burrows
(Rauch 1988). Females lay 1–6 eggs (most commonly 2–3), which is highly dependent on female body
condition and food availability (see subspecies cristatus, hassi, and trillmichi for additional data). Eggs
are left to incubate for three months (Laurie 1990; Laurie and Brown 1990a, 1990b). Individual female
iguanas typically reproduce once every two years (Vitousek 2009), or annually during periods of high
food abundance (Laurie 1990). Hatchlings emerge at a body mass of ca 50 g (Trillmich and Trillmich
1986).
Systems:ÊÊTerrestrial, Marine
Use and Trade
This species is listed in Appendix II of the Convention on International Trade in Endangered Species of
Wild Fauna and Flora (CITES). Wildlife trafficking is the third most profitable illegal activity in the world,
and although Ecuador has never declared export of live specimens of Amblyrhynchus cristatus for
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
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commercial trade (CITES trade data, UNEP-WCMC 2018), they are known to exist in the pet trade. Four
smuggling cases with prosecutions occurred between 2010 and 2015 (Auliya et al. 2016). While not
significantly reducing the population currently, their entry into the pet trade is of concern.
Threats (see Appendix for additional information)
Marine Iguanas are threatened by extreme fluctuations in population size caused by periodic El Niño
events (30–50% average mortality in the region, and up to 90% are known). Deaths are due to starvation
following a rapid temperature-driven change in the algal community (Wikelski et al. 1996). During El
Niño events, warm water from the Gulf of Panama flows toward the Galápagos and the nutrient
upwelling is suppressed, which results in the proliferation of brown algae (e.g., Giffordia mitchelliae)
that is not easily digestible by iguanas and may be toxic. The largest animals of each subpopulation
starve first (Wikelski and Trillmich 1997, Wikelski et al. 1997, Wikelski 2005) followed by smaller
individuals during these periods. Food shortages during El Niño events can lead to the unusual
phenomenon of shrinking in body length within just a few months (Wikelski and Thom 2000), apparently
facilitated by absorption of their own bone matter. Predictions that climate change may increase the
severity and frequency of El Niño events (Timmermann et al. 1999, Cai et al. 2014) suggest that some
subpopulations could be removed entirely.
On several large islands (Isabela, Santiago, Santa Cruz and Baltra, Floreana, San Cristóbal) and satellite
cays, there is an ongoing significant threat to Marine Iguanas from invasive alien predators, particularly
cats (Felis catus) and rats (Rattus rattus, R. norwegicus), as well as free-roaming domestic dogs (Canis
familiaris, Kruuk and Snell 1981) and pigs (Sus domesticus; Phillips et al. 2012). For several decades, the
presence of cats has been associated with a lack of hatchling and juvenile Marine Iguanas (Laurie 1983,
Cayot et al. 1994, MacLeod and Steinfartz 2016). Predation has also been directly confirmed at several
locations on Isabela and Santa Cruz (Laurie 1983, Konecny 1983). The survival of hatchlings in colonies
affected by predators is alarmingly low: 1% at a cat-affected colony on Santa Cruz compared to 53% at
an unaffected colony on Santa Fe (Laurie 1983). Rats likely pose the most significant threat to young
Marine Iguanas on islands where other food sources for the rats are scarce as on the small cays (e.g.,
Pinzón, Cayot et al. 1994). The total adult population of iguanas on affected islands is estimated at ca
7,100–57,000 which constitutes ca 20 and 30% of the total adult iguana population.
The Galápagos has seen a dramatic recent increase in both tourists and residents living on the islands
and adversely affecting the ecosystem. Approximately 25,000 people live among five islands (Toral-
Granda et al. 2017), though this figure likely does not include illegal residents seeking work in the
tourism industry. The total number of tourists arriving in Galápagos each year has also increased from
11,765 in 1979 to 224,755 tourists in 2015, a 19-fold increase. Between 2000 and 2015, average annual
tourism growth was 8.2% and the number of sites visited has increased to 169. The nature of tourism
has also changed, from being historically boat-based, to now being significantly land-based (on the
inhabited islands) (Toral-Granda et al. 2017). Tourist presence and intensity has been shown to have a
significant overall negative effect on immunological capability, endocrine response, and oxidative stress
in Marine Iguanas (French et al. 2010, 2017).
Cargo ship traffic has risen to supply the larger resident and tourist population, and this has brought an
increase in various types of pollution, habitat degradation, and an increased chance of invasive
terrestrial species introductions and emergent mosquito-borne diseases. Additionally, the potential for
aquatic invaders on ship hulls and in ballast water may pose a threat to the Marine Iguanas’ food supply
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
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(Toral-Granda et al. 2017). An unusual mortality (62% loss) on Santa Fé was recorded in 2001 following a
diesel and oil spill from a tanker that ran aground near the island of San Cristóbal (Wikelski et al. 2002).
Other subpopulations may have well been affected, but this was not recorded due to lack of long-term
monitoring for most islands. Notable is that just trace amounts of oil around Santa Fé caused this
mortality, indicating the extreme sensitivity of Marine Iguanas to such pollution. It is thought that the
symbiotic bacteria within the gut of the iguanas that are essential for proper digestion (Mackie et al.
2004) were negatively affected/removed by this exposure, resulting in the iguanas being unable to
digest their food. Several other diesel and oil spills have occurred since 2001 on Santa Cruz and San
Cristóbal.
On islands with permanent human settlements (Santa Cruz, San Cristóbal, Isabela, and Floreana),
municipal waste incineration of organic waste and plastics in open dump areas is a potential source of
unintentionally), municipal waste incineration of organic waste and plastics in open dump areas is a
potential source of unintentionally-produced persistent organic pollutants such as dioxins and furans.
Over 50% of the currently used pesticides applied in the agriculture zone were identified as endocrine-
disrupting chemicals, underscoring potential health effects in the endemic fauna (Alava et al. 2014).
Widespread marine plastic debris and micro-plastic pollution may be an emerging threat to Marine
Iguanas and their food source.
Conservation Actions (see Appendix for additional information)
The entire Marine Iguana distribution is included in three protected areas: Galápagos National Park and
National Marine Reserve, Galápagos Islands Man and Biosphere Reserve (UNESCO), and Galápagos
Islands World Heritage Site. Because the Galápagos is a high tourism area, it has attracted large numbers
of migrants from the Ecuadorian mainland seeking tourist industry jobs. To curb population increase,
Ecuador enacted a new law (Ley Orgánica de Régimen Especial para la Conservación y Desarrollo
Sustentable de la Provincia de Galápagos: LOREG) requiring a special visa to visit the Galápagos, and
there are strict limits on who can move there permanently (Strahm and Patry 2010).
Several eradication programmes have occurred in the Galápagos, including feral goats from several
islands, cats from Baltra and Venecia, and Black Rats from Seymour Norte and Bainbridge #4 (Phillips et
al. 2012). Increased efforts to eradicate or control cats, dogs, rats, and pigs to benefit all subpopulations
of Marine Iguanas is sorely needed. The impact of rats is less well understood, however, it was
documented that more hatchlings than normal were observed following a nearly complete eradication
of Black Rats from Pinzón in 1988 (Cayot et al. 1994).
Conservation and research actions recommended for the species include an improved knowledge of
population size, trends, distribution, factors limiting population size, habitat trends, and invasive species
management. Some populations are of particular conservation concern and further research on the
impact of low effective population size is recommended. Research to understand the impact of warming
waters (climate change and El Niño) on individual algae species, along with other factors affecting algae
community composition and iguana foraging dynamics, is recommended (Shepherd and Hawks 2005,
Vinueza et al. 2006, Tomkins and Wolff 2017). An increased understanding of the effect of widespread
oceanic pollution, including oil spills and micro-plastics, on Marine Iguanas and their micro-biota (which
enable effective digestion) is also needed. Plastic debris ranks as one of the most abundant and
persistent solid wastes at sea and shorelines, representing 25% of the total marine debris collected
during beach cleanups in the Galápagos (Alava et al. 2014). Improved biosecurity measures to prevent
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
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disease introductions, such as West Nile Virus, avian malaria, and other are also recommended. Ongoing
monitoring for introduced pathogens in Galápagos reptiles and other fauna is needed (Bataille et al.
2009; Eastwood et al. 2013, 2014).
Credits
Assessor(s): MacLeod, A., Nelson, K.N. & Grant, T.D.
Reviewer(s): Perry, G.
Contributor(s): Steinfartz, S.
Authority/Authorities: IUCN SSC Iguana Specialist Group
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
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Citation
MacLeod, A., Nelson, K.N. & Grant, T.D. 2020. Amblyrhynchus cristatus (errata version published in
2020). The IUCN Red List of Threatened Species 2020: e.T1086A177552193.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T1086A177552193.en
Disclaimer
To make use of this information, please check the Terms of Use.
External Resources
For Supplementary Material, and for Images and External Links to Additional Information, please see the
Red List website.
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13
Appendix
Habitats
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Habitat Season Suitability Major
Importance?
3. Shrubland -> 3.5. Shrubland - Subtropical/Tropical Dry Breeding
season
Suitable Yes
9. Marine Neritic -> 9.2. Marine Neritic - Subtidal Rock and Rocky Reefs Resident Suitable Yes
12. Marine Intertidal -> 12.1. Marine Intertidal - Rocky Shoreline Resident Suitable Yes
12. Marine Intertidal -> 12.2. Marine Intertidal - Sandy Shoreline and/or
Beaches, Sand Bars, Spits, Etc
Breeding
season
Suitable Yes
12. Marine Intertidal -> 12.3. Marine Intertidal - Shingle and/or Pebble
Shoreline and/or Beaches
Resident Marginal -
12. Marine Intertidal -> 12.4. Marine Intertidal - Mud Flats and Salt Flats Resident Marginal -
Use and Trade
(http://www.iucnredlist.org/technical-documents/classification-schemes)
End Use Local National International
Pets/display animals, horticulture No No Yes
Threats
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Threat Timing Scope Severity Impact Score
1. Residential & commercial development -> 1.1.
Housing & urban areas
Ongoing Minority (50%) Slow, significant
declines
Low impact: 5
Stresses: 1. Ecosystem stresses -> 1.2. Ecosystem degradation
2. Species Stresses -> 2.1. Species mortality
6. Human intrusions & disturbance -> 6.1.
Recreational activities
Ongoing Minority (50%) Causing /could
cause fluctuations
Low impact: 5
Stresses: 2. Species Stresses -> 2.2. Species disturbance
2. Species Stresses -> 2.3. Indirect species effects
8. Invasive and other problematic species, genes &
diseases -> 8.1. Invasive non-native/alien
species/diseases -> 8.1.2. Named species (Rattus
rattus)
Ongoing Majority (50-
90%)
Slow, significant
declines
Medium
impact: 6
Stresses: 2. Species Stresses -> 2.1. Species mortality
2. Species Stresses -> 2.3. Indirect species effects
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
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8. Invasive and other problematic species, genes &
diseases -> 8.1. Invasive non-native/alien
species/diseases -> 8.1.2. Named species (Rattus
norvegicus)
Ongoing Minority (50%) Slow, significant
declines
Low impact: 5
Stresses: 2. Species Stresses -> 2.1. Species mortality
2. Species Stresses -> 2.3. Indirect species effects
8. Invasive and other problematic species, genes &
diseases -> 8.1. Invasive non-native/alien
species/diseases -> 8.1.2. Named species (Sus
domesticus)
Ongoing Majority (50-
90%)
Slow, significant
declines
Medium
impact: 6
Stresses: 2. Species Stresses -> 2.1. Species mortality
2. Species Stresses -> 2.3. Indirect species effects
8. Invasive and other problematic species, genes &
diseases -> 8.1. Invasive non-native/alien
species/diseases -> 8.1.2. Named species (Felis catus)
Ongoing Minority (50%) Rapid declines Medium
impact: 6
Stresses: 2. Species Stresses -> 2.1. Species mortality
2. Species Stresses -> 2.3. Indirect species effects
8. Invasive and other problematic species, genes &
diseases -> 8.1. Invasive non-native/alien
species/diseases -> 8.1.2. Named species (Canis
familiaris)
Ongoing Minority (50%) Rapid declines Medium
impact: 6
Stresses: 2. Species Stresses -> 2.1. Species mortality
9. Pollution -> 9.2. Industrial & military effluents ->
9.2.1. Oil spills
Future Minority (50%) Causing/could
cause fluctuations
Low impact: 3
Stresses: 1. Ecosystem stresses -> 1.3. Indirect ecosystem effects
2. Species Stresses -> 2.1. Species mortality
9. Pollution -> 9.4. Garbage & solid waste Ongoing Majority (50-
90%)
Unknown Unknown
Stresses: 1. Ecosystem stresses -> 1.2. Ecosystem degradation
1. Ecosystem stresses -> 1.3. Indirect ecosystem effects
11. Climate change & severe weather -> 11.1. Habitat
shifting & alteration
Future Majority (50-
90%)
Causing/could
cause fluctuations
Low impact: 4
Stresses: 1. Ecosystem stresses -> 1.3. Indirect ecosystem effects
2. Species Stresses -> 2.1. Species mortality
11. Climate change & severe weather -> 11.3.
Temperature extremes
Ongoing Majority (50-
90%)
Causing/could
cause fluctuations
Medium
impact: 6
Stresses: 1. Ecosystem stresses -> 1.3. Indirect ecosystem effects
2. Species Stresses -> 2.1. Species mortality
2. Species Stresses -> 2.3. Indirect species effects
11. Climate change & severe weather -> 11.4. Storms
& flooding
Future Majority (50-
90%)
Causing/could
cause fluctuations
Low impact: 4
Stresses: 1. Ecosystem stresses -> 1.2. Ecosystem degradation
1. Ecosystem stresses -> 1.3. Indirect ecosystem effects
2. Species Stresses -> 2.1. Species mortality
2. Species Stresses -> 2.3. Indirect species effects
12. Other options -> 12.1. Other threat Future Majority (50-
90%)
Unknown Unknown
Stresses: 2. Species Stresses -> 2.1. Species mortality
2. Species Stresses -> 2.3. Indirect species effects
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T1086A177552193.en
15
Conservation Actions in Place
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Conservation Action in Place
In-place research and monitoring
Action Recovery Plan: No
Systematic monitoring scheme: No
In-place land/water protection
Conservation sites identified: No
Percentage of population protected by PAs: 91-100
Area based regional management plan: No
Occurs in at least one protected area: Yes
Invasive species control or prevention: Yes
In-place species management
Harvest management plan: No
Successfully reintroduced or introduced benignly: No
Subject to ex-situ conservation: No
In-place education
Subject to recent education and awareness programmes: No
Included in international legislation: Yes
Subject to any international management / trade controls: Yes
Conservation Actions Needed
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Conservation Action Needed
1. Land/water protection -> 1.2. Resource & habitat protection
2. Land/water management -> 2.2. Invasive/problematic species control
5. Law & policy -> 5.1. Legislation -> 5.1.3. Sub-national level
Research Needed
(http://www.iucnredlist.org/technical-documents/classification-schemes)
Research Needed
1. Research -> 1.2. Population size, distribution & trends
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T1086A177552193.en
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Research Needed
1. Research -> 1.3. Life history & ecology
1. Research -> 1.5. Threats
2. Conservation Planning -> 2.2. Area-based Management Plan
3. Monitoring -> 3.1. Population trends
3. Monitoring -> 3.4. Habitat trends
Additional Data Fields
Distribution
Estimated area of occupancy (AOO) (km²): 4368
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): Unknown
Estimated extent of occurrence (EOO) (km²): 56647
Continuing decline in extent of occurrence (EOO): No
Extreme fluctuations in extent of occurrence (EOO): No
Continuing decline in number of locations: Unknown
Extreme fluctuations in the number of locations: Unknown
Lower elevation limit (m): 0
Upper elevation limit (m): 400
Lower depth limit (m): 0
Upper depth limit (m): 30
Population
Number of mature individuals: 19,800-210,000
Continuing decline of mature individuals: Yes
Extreme fluctuations: Yes
Population severely fragmented: Yes
No. of subpopulations: 11
Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: Unknown
All individuals in one subpopulation: No
No. of individuals in largest subpopulation: 12000-96000
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T1086A177552193.en
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Habitats and Ecology
Continuing decline in area, extent and/or quality of habitat: Yes
Generation Length (years): 6-8
Movement patterns: Not a Migrant
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T1086A177552193.en
18
Errata
Errata reason: This erratum was created to correct the Assessor name "Nelson, K." to "Nelson, K.N.".
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T1086A177552193.en
19
The IUCN Red List of Threatened Species™
ISSN 2307-8235 (online)
IUCN 2020: T1086A177552193
Scope(s): Global
Language: English
The IUCN Red List Partnership
The IUCN Red List of Threatened Species™ is produced and managed by the IUCN Global Species
Programme, the IUCN Species Survival Commission (SSC) and The IUCN Red List Partnership.
The IUCN Red List Partners are: Arizona State University; BirdLife International; Botanic Gardens
Conservation International; Conservation International; NatureServe; Royal Botanic Gardens, Kew;
Sapienza University of Rome; Texas A&M University; and Zoological Society of London.
THE IUCN RED LIST OF THREATENED SPECIES™
© The IUCN Red List of Threatened Species: Amblyrhynchus cristatus – published in 2020.
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20
... 65,000). This, along with the very recent divergence of the two considered populations (0.03 Mya, Fig. 5), is consistent with recent and ongoing gene flow among different A. cristatus populations, facilitated by the species' high mobility (MacLeod et al., 2019), and with Conolophus ancestral population presenting a stronger and prolonged population structure. ...
... Additionally, the marine iguana may have experienced historical phases of demographic fluctuations with severe population decline due to unpredictable yet recurring famine (during El Niño) and feast (during La Niña) events (MacLeod et al., 2019). ...
Article
Full-text available
Galapagos iguanas are a monophyletic group endemic to the Galapagos archipelago, comprising the marine iguana Amblyrhynchus cristatus and three species of land iguanas: Conolophus subcristatus, C. pallidus and C. marthae. The biogeographic history of the land species in relation to their current distributions remains un-certain, in particular the origins of C. marthae, which is restricted to a small area of the northern part of IsabelaIsland. The classification of C. pallidus as a separate species has also been debated. We analyzed DNA sequences (RADseq) to reconstruct demographic histories of selected local populations of all Gal apagos iguana species and estimate their divergence times within a multispecies coalescent framework. Our results indicate an early date for the colonization of Galapagos by iguanas, relative to island formation, at ca. 10Mya, and support a recent split of C. marthae via allopatric speciation, after the emergence of Isabela Island, at ca. 0.57 Mya. We find contrasting demographic histories in C. marthae and the syntopic population of C. subcristatus, suggesting competitive interaction between these species. We also confirm that the divergence of C. pallidus from C. subcristatus is recent (0.09 Mya) and close in time to the split between populations of C. subcristatus fromdifferent islands. Our genetic data support recent census estimates indicating a relatively small current effectivepopulation size (Ne) in all the studied populations. Our findings shed light on the evolutionary history of Galapagos iguanas and emphasize the need for targeted conservation strategies.
... Marine iguanas (Amblyrhynchus cristatus) are endemic animals from the Galapagos Islands, Ecuador, specialized about 4.5 million years ago to be the world's only sea lizards able to survive by grazing red and green algae [1]. With a population of approximately 19,800-210,000 specimens, these reptiles are vulnerable to extinction due to anthropogenic factors including climatic change, nonnative predators, and plastic and oil pollution [2]. Therefore, multidisciplinary efforts are needed to preserve this iconic species. ...
... The estimated genomic copies (GC) of ARGs and MGEs were computed with the formula (1) considering a cycle threshold (Ct) cutoff of 32. The relative abundance (RA) was calculated by dividing the GC of a given gene by the GC of the 16S rRNA gene, as shown in formula (2). Shannon index, Bray Curtis dissimilarity, and differentially abundant features were calculated as described for the microbiome analyses. ...
Article
Full-text available
Background Understanding the natural microbiome and resistome of wildlife from remote places is necessary to monitor the human footprint on the environment including antimicrobial use (AU). Marine iguanas are endemic species from the Galapagos Islands where they are highly affected by anthropogenic factors that can alter their microbiota as well as their abundance and diversity of antimicrobial-resistant genes (ARGs). Thus, this study aims to apply culture-independent approaches to characterize the marine iguana’s gut metagenomic composition of samples collected from the uninhabited islands Rabida (n = 8) and Fernandina (Cabo Douglas, n = 30; Punta Espinoza, n = 30). Fresh feces from marine iguanas were analyzed through SmartChip RT-PCR, 16S rRNA, and metagenomic next-generation sequencing (mNGS) to identify their microbiome, microbial-metabolic pathways, resistome, mobilome, and virulome. Results The marine iguana’s gut microbiome composition was highly conserved despite differences in ecological niches, where 86% of taxa were shared in the three locations. However, site-specific differences were mainly identified in resistome, mobilome, virulorome, and metabolic pathway composition, highlighting the existence of factors that induce microbial adaptations in each location. Functional gut microbiome analyses revealed its role in the biosynthesis and degradation of vitamins, cofactors, proteinogenic amino acids, carbohydrates, nucleosides and nucleotides, fatty acids, lipids, and other compounds necessary for the marine iguanas. The overall bacterial ARG abundance was relatively low (0.006%); nevertheless, the presence of genes encoding resistance to 22 drug classes was identified in the iguana’s gut metagenome. ARG-carrying contig and co-occurrence network analyses revealed that commensal bacteria are the main hosts of ARGs. Taxa of public health interest such as Salmonella, Vibrio, and Klebsiella also carried multidrug-resistance genes associated with MGEs which can influence the dissemination of ARGs through horizontal gene transfer. Conclusion Marine iguanas depend on the gut microbiome for the biosynthesis and degradation of several compounds through a symbiotic relationship. Niche-specific adaptations were evidenced in the pool of microbial accessory genes (i.e., ARGs, MGEs, and virulence) and metabolic pathways, but not in the microbiome composition. Culture-independent approaches outlined the presence of a diverse resistome composition in the Galapagos marine iguanas from remote islands. The presence of AR pathogens in marine iguanas raises concerns about the dispersion of microbial-resistant threats in pristine areas, highlighting wildlife as sentinel species to identify the impact of AU.
... Regarding iguanas, rising sea surface temperatures driven by El Niño events-which are increasing in the context of climate change (Cai et al., 2014)-disrupt the supply of seaweed. Since seaweed is the main food source for iguanas, its loss can cause up to 90% of the population to die from starvation during these events (MacLeod et al., 2020). Concerning the latter threat, sea turtles and saltwater crocodiles have temperature-dependent sex determination (Woodward & Dickson, 1993;Tezak et al., 2020;Patrıćio et al., 2021), and therefore climate-change-driven temperature rises could affect sex bias within these populations. ...
... This is possible because the counting of iguanas from aerial imagery by experts has already been validated against traditional ground-based approaches (Varela-Jaramillo et al., 2023). This work is an important contribution to our overall goal of addressing the populationsize data-gap that currently hampers effective conservation in this species (MacLeod et al., 2020). ...
Preprint
Population surveys are vital for wildlife management, yet traditional methods often demand excessive time and resources, leading to data gaps for many species. Modern technologies such as drones can facilitate field surveys but may also increase data analysis challenges. Citizen Science (CS) can address this issue by engaging non-specialists for data collection and analysis. We evaluated CS for population monitoring using the endangered Galapagos marine iguana as a case study, assessing online volunteers' ability to detect and count animals in aerial images. Comparing against a Gold Standard dataset of expert counts in 4345 images, we explored optimal aggregation methods from CS inputs, considering image quality and filtering data from infrequent and anonymous participants. During three phases of our project - hosted on the Zooniverse platform - over 13,000 volunteers made 1,375,201 classifications from 57,838 aerial images; each being independently classified 20 (phases 1 & 2) or 30 (phase 3) times. Volunteers achieved 68% to 94% accuracy in detecting iguanas, with more false negatives than false positives. Image quality strongly influenced accuracy; by excluding data from suboptimal pilot-phase images, volunteers counted with 90% to 92% of accuracy. For detecting presence or absence of iguanas, the commonly used "majority vote" aggregation approach (where the answer selected is that given by the majority of individual inputs) produced less accurate results than when a minimum threshold of five (from the 20/30 independent classifications) was used. For counting iguanas, HDBSCAN clustering yielded the best results. Excluding inputs from anonymous and inexperienced volunteers decreased accuracy. We conclude that online volunteers can accurately identify and count marine iguanas from drone images, though a tendency to underestimate warrants further consideration. CS-based data analysis is faster than manual counting but still resource-intensive, underscoring the need to develop a Machine Learning approach.
Article
Full-text available
Marine iguanas occasionally face severe food shortages because of algal dieback during El Niño events. Research on their adaptations to these periods has highlighted their unique ability to shrink in body length, which reduces their energetic needs. Additional mechanisms, like sustaining lower body temperatures and metabolic rates, could potentially also lower energy consumption, but have never been examined. We measured 665 iguanas over an 11‐year period including three El Niño events, and examined how heart rates (a proxy for metabolic rates) and body temperatures change with sea‐surface temperature oscillations (Oceanic Niño Index, ONI). Heart rate (adjusting for body size, temperature, season, and study site) was negatively correlated with ONI and lower during El Niño, whereas the adjusted body temperature did not correlate with ONI or differ between El Niño and other periods. We therefore hypothesize that marine iguanas can depress their metabolic rates in response to the harsh conditions, an adaptation that is complementary to shrinking and may further enhance their survival through periods of limited food. Direct metabolic measurements are needed to test this hypothesis.
Preprint
Galápagos iguanas are a monophyletic group endemic to the Galápagos archipelago, comprising the marine iguana Amblyrhynchus cristatus and three species of land iguanas: Conolophus subcristatus, C. pallidus and C. marthae. The biogeographic history of the land species in relation to their current distributions remains uncertain, in particular the origins of C. marthae, which is restricted to a small area of the western part of Isabela Island. The classification of C. pallidus as a separate species has also been debated. We analyzed Restriction sites Associated DNA sequences (RADseq) to reconstruct demographic histories of selected local populations of all Galápagos iguana species and estimate their divergence times within a multispecies coalescent framework. Our results indicate an early date for the colonization of Galápagos by iguanas, relative to island formation, at ca. 10 Mya, and support a recent split of C. marthae via allopatric speciation, after the emergence of Isabela Island, at ca. 0.57 Mya. We find contrasting demographic histories in C. marthae and the syntopic population of C. subcristatus, suggesting competitive interaction between these species. We also confirm that the divergence of C. pallidus from C. subcristatus is recent and close in time to the split between populations of C. subcristatus from different islands. Our genetic data support recent census estimates indicating a relatively small current effective population size (Ne) in all the studied populations. Our findings shed light on the evolutionary history of Galápagos iguanas and emphasize the need for targeted conservation strategies.
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(1) Annual survival rates of marine iguanas (Amblyrhynchus cristatus) on Galapagos were estimated using recapture and resightings of marked individuals. (2) There was 60-70% overall mortality due to starvation, during the 1982-1983 El Nino-Southern Oscillation Event. (3) Adult males suffered higher mortality than adult females over the period of food shortage, but size explained most of the difference in mortality between the sexes. (4) There was a cost of breeding for females, in terms of survival, in 1 of the 5 years of the study. (5) Larger hatchlings and yearlings survived better over the El Nino period than smaller ones, and there was selection for 2 and 3-year-olds that weighed more in 1981, at emergence, or at 1-year-old, respectively.
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