Galápagos Archipelago IMMA
Size in Square Kilometres
139 517 km2
Qualifying Species and Criteria
Galápagos fur seal – Arctocephalus galapagoensis
Criterion A; B (1)
Galápagos sea lion – Zalophus wollebaeki
Criterion A; B (1)
Blue whale – Balaenoptera musculus
Criterion A; C (1, 2)
Bryde’s whale – Balaenoptera edeni
Criterion B (2)
Humpback whale – Megaptera novaeangliae
Criterion C (1)
Sperm whale – Physeter macrocephalus
Criterion A; B (2)
Killer whale – Orcinus orca
Criterion B (2)
Marine Mammal Diversity
Criterion D (2)
Globicephala macrorhynchus, Grampus griseus, Risso’s dolphin, Tursiops truncatus, Delphinus delphis, Stenella coeruleoalba, Ziphius cavirostris,
Kogia sima, Stenella attenuata, Stenella longirostris
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Summary
Oceanographic conditions around the Galápagos Archipelago IMMA are conducive to high levels of biological productivity, species diversity, and marine endemism. These waters have been designated as a marine reserve by the government of Ecuador and as a Natural World Heritage Site by UNESCO. Numerous scientific expeditions and other research in the last 40 years have demonstrated the importance of the Galápagos Archipelago for marine mammals. The islands feature populations of two endangered and endemic pinnipeds, the Galápagos fur seal (Arctocephalus galapagoensis) and the Galápagos sea lion (Zalophus wollebaeki). The unique local habitats created by these oceanic islands are also breeding and feeding grounds for Endangered (EN) blue whales (Balaenoptera musculus) migrating from Chile, and Southern humpback whales (Megaptera novaeangliae australis) migrating from the Antarctic Peninsula. The archipelago also hosts aggregations of Bryde’s whales (Balaenoptera edeni brydei), vulnerable sperm whales (Physeter macrocephalus), and killer whales (Orcinus orca) inhabiting the eastern tropical Pacific. The rich oceanic waters surrounding the archipelago also support aggregations of a high diversity of medium and small cetacean species.
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
The Galápagos Archipelago contains habitat important for the survival and recovery of four marine mammal species whose conservation status is of concern under the IUCN Red List of Threatened species. The population of Galápagos fur seals (Arctocephalus galapagoensis), listed as Endangered (EN), is estimated at about 10,000 mature individuals and considered to be declining (Trillmich, 2015a). Similarly, the population of Galápagos sea lions (Zalophus wollebaeki), listed as Endangered, is also estimated at about 10,000 mature individuals and considered to be declining (Trillmich, 2015b). Subsequent to these IUCN assessments, more recent data suggest that the populations of both species have somewhat increased, but they continue to be subject to strong inter-annual fluctuations associated with El Niño and La Niña events (Páez-Rosas et al., 2021).
Blue whales (Balaenoptera musculus) have also been assessed as Endangered (EN) on the IUCN Red List of Threatened species (Cooke, 2019). The global estimate for the number of mature blue whales is thought to be in the range 5,000-15,000 individuals, with an increasing trend, while the Chilean blue whale subpopulation is thought to be in the low hundreds (300-450 individuals), with an uncertain population trend (Cooke, 2019). Sperm whales (Physeter macrocephalus) are listed as Vulnerable (VU) on the IUCN Red List (Taylor, 2019). The current global mature population size is thought to be in the 100,000’s, with considerable uncertainty in population trend (Taylor, 2019). The population of sperm whales inhabiting the eastern tropical Pacific was estimated at 22,666 individuals in 1993 (Wade and Gerrodette, 1993) and the number of animals using Galápagos waters was estimated at 1,254 in 1990 (Whitehead et al., 1997). However, the Whitehead et al. (1997) study, as well as a more recent study spanning the period 1985-2014 (Cantor et al., 2017), revealed strong inter-decadal fluctuations in the number of animals that visit Galápagos as a result of movements in and out of the archipelago.
Criterion B: Distribution and Abundance
Sub-criterion B1: Small and Resident Populations
The Galápagos Archipelago encompasses the primary breeding and feeding habitat for both Galápagos fur seals and Galápagos sea lions (Salazar, 2002). As noted prior, however, oceanographic events such as El Niño and La Niña result not only in strong interannual fluctuations in the populations of these pinnipeds but also in their distribution at sea. Indeed, distant haul-outs and even small temporary breeding colonies of both species have been reported outside Galápagos during anomalous years (e.g., Palacios et al., 1997, Félix et al., 2007, Aurioles-Gamboa et al., 2004, Ceballos et al., 2010, Quintana-Rizzo et al., 2017, Páez-Rosas et al., 2017). Similarly, an influx of atypical pinniped species has been reported in Galápagos during these strong perturbations (e.g., Páez-Rosas et al., 2020, Alava et al., 2022). In all cases, these redistributions appear to be temporary.
Sub-criterion B2: Aggregations
A quantitative analysis of cetacean community structure in the Galápagos demonstrated that a combination of physical and biological factors results in a variety and persistence of ecological niches for a set of species that are numerically abundant within the archipelago (Palacios, 2003). Among these, the Bryde’s whale (Balaenoptera edeni brydei) is seen in feeding aggregations especially on the western part of the archipelago (Palacios et al., 2002, Denkinger et al., 2013), as well as off San Cristóbal Island, in the eastern part (Biggs et al., 2017). Aggregations of female and immature sperm whales (Physeter macrocephalus) are seen in the deeper waters of the archipelago, although their numbers wax and wane over the years as groups of animals move in and out of the area (Whitehead et al., 1997, Cantor et al., 2017).
Killer whales (Orcinus orca) have naturally low abundance and roam broadly in the eastern tropical Pacific. However, they are regularly seen off the Galápagos, and most encounters include observations of feeding. Galápagos harbours abundant populations of prey for killer whales, including teleost and elasmobranch fishes, sea turtles, pinnipeds, and cetaceans, that are otherwise sparsely distributed in the broader eastern tropical Pacific region (Denkinger et al., 2020).Killer whales are commonly seen on the western side of the archipelago, where they are seen preying on a very wide variety of marine species, but they are also regularly observed off Baltra, Santa Cruz, and the San Cristóbal Islands (Denkinger et al., 2020).
Criterion C: Key Life Cycle Activities
Sub-criterion C1: Reproductive Areas
The Galápagos Archipelago is part of the low-latitude range of Chilean blue whales, where they are observed to breed annually during the austral winter (Palacios, 1999; Biggs et al., 2017; Hucke-Gaete et al., 2018). The Galápagos Archipelago is also part of the low-latitude range of Southern Hemisphere humpback whales from IWC Breeding Stock G, where they breed annually during the austral winter (Félix et al., 2011; Biggs et al., 2017).
Sub-criterion C2: Feeding Areas
The Galápagos Archipelago is part of the low-latitude range of Chilean blue whales, where they are observed to feed annually during the austral winter (Palacios, 1999; Biggs et al., 2017; Hucke-Gaete et al., 2018).
Criterion D: Special Attributes
Sub-criterion D2: Diversity
Twelve qualifying species denotes the evidence that the Galápagos Archipelago IMMA supports an important diversity of marine mammal species. An analysis of community structure based on cetacean sightings data demonstrated that the high diversity of species regularly present in Galápagos is supported by a combination of physical and biological factors that result in a variety and persistence of ecological niches (core habitats) around the archipelago (Palacios, 2003). A separate study of cetacean strandings in Galápagos indicated a pattern consistent with the sighting record (Palacios et al., 2004). Additional studies have documented cetacean species occurrence in Galápagos waters (Day, 1994, Smith and Whitehead, 1999, Palacios et al., 2002, Denkinger et al., 2013). In addition to the species mentioned prior, under the previous criteria descriptions, short-finned pilot whales (Globicephala macrorhynchus) and Risso’s dolphins (Grampus griseus) are commonly found in offshore waters, especially along the steep slopes of the western side of the archipelago (Palacios et al., 2002). Common bottlenose dolphins (Tursiops truncatus) are the most commonly sighted species in nearshore waters of the archipelago, with aggregations being reported from the waters between Isabela and Floreana Islands, north of Santa Cruz Island, in the Bolivar Channel between Fernandina and Isabela Islands, between Santiago and Pinzón Islands, and around the islets of Roca Redonda, Wolf, and Darwin (Palacios et al., 2002). This coastal distribution is consistent with the island-associated ecotype that has been reported around other oceanic islands, and it is possible that with more research, common bottlenose dolphins may qualify for Criterion B1 (Small and Resident Populations) in a future assessment. Finally, large aggregations of short-beaked common dolphins (Delphinus delphis) and striped dolphins (Stenella coueruleoalba) are common in offshore waters of the archipelago, especially in the western and northern parts where topographic upwelling of the Equatorial Undercurrent is strongest (Palacios et al., 2002, Palacios, 2003, Palacios and Forney, 2008). It is also probable that at least half a dozen beaked whale species occur in Galápagos waters but these are reported only infrequently due to their cryptic behaviour and difficulty in identifying species at sea. While the relative sighting frequency of each species may vary between studies, they all conclude that the Galápagos Archipelago is an area that attracts and sustains an outstanding diversity of marine mammals.
Supporting Information
Alava, J.J., Riofrío-Lazo, M., Reygondeau, G., Rosero, P., Avila, I.C., Lara, D., Gil, F., Yaipen-Llanos, C. F., Elorriaga-Verplancken, F. R. and Páez-Rosas, D. 2022. ‘Southern elephant seals (Mirounga leonina) in the Galapagos Islands and the eastern tropical Pacific amid ocean environmental changes: towards a habitat suitability index’. Aquatic Mammals, 48(5): 418–431.
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