Endemic species predation by the introduced smooth-billed ani in Galápagos

Cooke, Sophia C.; Anchundia, David; Caton, Emma; Haskell, Lucy E.; Jäger, Heinke; Kalki, Yatindra; Mollá, O.; Rodríguez, Jacqueline; Schramer, Tristan D.; Walentowitz, Anna; Feßl, Birgit

doi:10.1007/s10530-020-02251-3

Cited by 8 publications

(6 citation statements)

References 15 publications

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“…Contrary to other countries in the region -whether mega-diverse or not (Heringer et al 2021;Adelino et al 2021;Duboscq-Carra et al 2021), Ecuadorian institutional authorities, at least in the Galapagos Islands, have invested actively in invasive species management actions. One of the reasons is the body of research about the massive impact that invasive species have on the Galapagos resident biota (Jäger et al 2009;Jäger et al 2013;Rivas-Torres and Rivas 2018;Cooke et al 2020), triggering investment to control or eradicate these species. However, ecological damage is more difficult to monetize and consequently, fewer costs are reported.…”

Section: Discussionmentioning

confidence: 99%

Economic costs of biological invasions in Ecuador: the importance of the Galapagos Islands

Ballesteros‐Mejia¹,

Angulo²,

Diagne³

et al. 2021

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Biological invasions, as a result of human intervention through trade and mobility, are the second biggest cause of biodiversity loss. The impacts of invasive alien species (IAS) on the environment are well known, however, economic impacts are poorly estimated, especially in mega-diverse countries where both economic and ecological consequences of these effects can be catastrophic. Ecuador, one of the smallest mega-diverse countries, lacks a comprehensive description of the economic costs of IAS within its territory. Here, using "InvaCost", a public database that compiles all recorded monetary costs associated with IAS from English and Non-English sources, we investigated the economic costs of biological invasions. We found that between 1983 and 2017, the reported costs associated with biological invasions ranged between US$86.17 million (when considering only the most robust data) and US$626 million (when including all cost data) belonging to 37 species and 27 genera. Furthermore, 99% of the recorded cost entries were from the Galapagos Islands. From only robust data, the costliest identified taxonomic group was feral goats (Capra hircus; US$20 million), followed by Aedes mosquitoes (US$2.14 million) while organisms like plant species from the genus Rubus, a parasitic fly (Philornis downsi), black rats (Rattus rattus) and terrestrial gastropods (Achatina fulica) represented less than US$2 million each. Costs of "mixed-taxa" (i.e. plants and animals) represented the highest (61% of total robust costs; US$52.44 million). The most impacted activity sector was the national park authorities, which spent about US$84 million. Results from robust data also revealed that management expenditures were the major type of costs recorded in the Galapagos Islands; however, costs reported for medical losses related to Aedes mosquitoes causing dengue fever in mainland Ecuador would have ranked first if more detailed information had allowed us to categorize them as robust data. Over 70% of the IAS reported for Ecuador did not have reported costs. These results suggest that costs reported here are a massive underestimate of the actual economic toll of invasions in the country.

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Section: Discussionmentioning

confidence: 99%

Economic costs of biological invasions in Ecuador: the importance of the Galapagos Islands

Ballesteros‐Mejia¹,

Angulo²,

Diagne³

et al. 2021

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“…Ani were introduced to the Galápagos during the 1960s to remove ticks from introduced cattle on Santa Cruz, spread to other islands during the 1990s, and the population of ca. 250,000 now consumes Darwin's Finch chicks, endemic Galápagos cricket (large painted locust, Gryllus abditus), Galápagos carpenter bee (Xylocopa darwini), Galápagos racer snake, Galápagos lava lizard (Microlophus albemarlensis) and a range of other endemic fauna [70][71][72]. They also consume and distribute the seeds of introduced blackberry and guava, and other species, thereby contributing to significant shifts in local ecosystem function [71,73,74].…”

Section: Discussionmentioning

confidence: 99%

“…250,000 now consumes Darwin's Finch chicks, endemic Galápagos cricket (large painted locust, Gryllus abditus), Galápagos carpenter bee (Xylocopa darwini), Galápagos racer snake, Galápagos lava lizard (Microlophus albemarlensis) and a range of other endemic fauna [70][71][72]. They also consume and distribute the seeds of introduced blackberry and guava, and other species, thereby contributing to significant shifts in local ecosystem function [71,73,74]. The finding that avian predation was the second leading cause of offspring mortality in Medium Tree Finch points to owl and/or ani, the only two avian predators on the island.…”

Section: Discussionmentioning

confidence: 99%

Nesting Success and Nesting Height in the Critically Endangered Medium Tree Finch (Camarhynchus pauper)

Kleindorfer

Common

Sumasgutner

2021

Birds

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When different introduced species across trophic levels (parasite, predator) invade island systems, they may pose significant threats to nesting birds. In this study, we measure nesting height and infer causes of offspring mortality in the critically endangered Medium Tree Finch (Camarhynchus pauper), an island endemic restricted to Floreana Island on the Galápagos Archipelago. Considering all nests at which a male built a nest, sang and attempted to attract a female (n = 222 nests), only 10.4% of nests produced fledglings (5% of nests had total fledging success, 5.4% of nests had partial fledging success). Of the 123 nests chosen by a female, 18.7% produced fledglings and of 337 eggs laid, 13.4% produced fledglings. Pairing success was higher for older males, but male age did not predict nesting success. All nests with chicks were infested with avian vampire fly larvae (Philornis downsi). We attributed the cause of death to avian vampire fly if chicks were found dead in the nest with fly larvae or pupae (45%) present. We inferred avian (either Asio flammeus galapagoensis or Crotophaga ani) predation (24%) if the nest was empty but dishevelled; and black rat (Rattus rattus) predation (20%) if the nest was empty but undamaged. According to these criteria, the highest nests were depredated by avian predators, the lowest nests by rats, and intermediate nests failed because of avian vampire fly larvae. In conclusion, there is no safe nesting height on Floreana Island under current conditions of threats from two trophic levels (introduced parasitic dipteran, introduced mammalian/avian predators; with Galápagos Short-Eared Owls being the only native predator in the system).

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“…T. b. galapagoensis larvae presumably preyed on other animals prior to the arrival of S. quinquefasciatus to the island, but our finding also suggests that the beetle larvae have not developed a tadpole specialisation-decreasing its potential as a natural control agent. A recent study showed that an introduced bird, the smooth-billed ani (Crotophaga ani), feeds on S. quinquefasciatus adults in Galápagos, but predation rates are also too low to have an effect on the frog's population size (Cooke et al 2020).…”

Section: Discussionmentioning

confidence: 99%

Eat and be eaten: trophic interactions of the introduced frog Scinax quinquefasciatus in anthropogenic environments in Galápagos

Moretta-Urdiales¹,

Ernst²,

Pontón-Cevallos³

et al. 2020

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While the Galápagos Archipelago is known for its endemic flora and fauna, many introduced species have also become naturalised there, especially on the human-inhabited islands. The only amphibian species known to have established on the islands, the Fowler’s snouted treefrog (Scinax quinquefasciatus), is thought to have arrived about two decades ago. Since then, this treefrog has substantially extended its range to the islands of Santa Cruz and Isabela. Our study explores the potential influence of this introduced amphibian on native trophic systems on Santa Cruz and identifies potential antagonists likely to control larval frog populations. To understand the impact of S. quinquefasciatus as a predator of local invertebrate fauna, we performed a stomach-content analysis of 228 preserved adult specimens from seven different localities on Santa Cruz. Of the 11 macroinvertebrate orders recorded, Lepidoptera constituted more than 60% of the contents. We also identified active predators of S. quinquefasciatus tadpoles: larvae of the endemic diving beetle (Thermonectus basillarus galapagoensis). To determine the efficiency of this predator, we conducted predator-prey experiments in ex situ conditions. Tadpole predation was highest after first exposure to the predator and significantly decreased over time. Our experimental results demonstrate that although T. b. galapagoensis larvae are effective tadpole predators, their feeding saturation rates are likely inadequate for frog population control. Our findings provide the first baseline data necessary to make informed ecological impact assessments and monitoring schemes on Santa Cruz for this introduced treefrog.

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Endemic species predation by the introduced smooth-billed ani in Galápagos

Cited by 8 publications

References 15 publications

Economic costs of biological invasions in Ecuador: the importance of the Galapagos Islands

Economic costs of biological invasions in Ecuador: the importance of the Galapagos Islands

Nesting Success and Nesting Height in the Critically Endangered Medium Tree Finch (Camarhynchus pauper)

Eat and be eaten: trophic interactions of the introduced frog Scinax quinquefasciatus in anthropogenic environments in Galápagos

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