Aim: Arthropods as vertebrate predators is generally overlooked in ecology due to the cryptic nature of these events, the relatively small size of arthropods, and the difficulty in finding published data. This study represents the largest global assessment of arthropods preying on vertebrates to provide a conceptual framework, identify global patterns, and provide a searchable database.

Location: Global. Time period: Present. Major taxa studied: Arthropods and vertebrates.

Methods: A systematic literature review was conducted.

Results: Nearly 1300 recorded observations were collated from 89 countries. Arthropod predators were from six classes and 80 families. Vertebrate prey were from five classes and 162 families. Spiders represented over half of all predatory events and were the main predator for all vertebrates except birds, which were preyed mostly upon by praying mantises. Over a third of all prey were amphibians, specifically frogs. Preyed reptiles were nearly all lizards, half of mammal prey were bats, nearly a third of fish were Cypriniformes, and half of bird prey were passerines. Predation by spiders were mainly documented from the U.S., Brazil, and Australia, and biased everywhere except the U.S.; insects were mainly from Europe, Australia, and the Americas, and biased toward North America; Amphibian events were mainly from the Americas and strongly biased everywhere, except for the U.S. and Australia; reptiles were mostly from the Americas and Australia, and biased towards the U.S. and Australia; birds were mainly from the Americas, Australia, and Europe, and biased towards Central America and Europe; mammals were mostly reported from North and Central America, Australia, and Asia, and strongly biased everywhere except Brazil.

Main conclusions: This study demonstrates that arthropods are an underestimated predator of vertebrates. Recognizing and quantifying these predator-prey interactions is vital for identifying patterns and the potential impact of these relationships on shaping vertebrate populations and communities.

An extensive literature search of vertebrate predation by arthropods was undertaken between November 2019 and June 2020. Scientific articles, reviews, bulletins, newsletters, books, theses, dissertations, government reports, and conference proceedings were searched using Google Scholar, BioOne, and Web of Science. The literature search was conducted using key search terms (e.g., arthropod, spider, insect, predation, prey, vertebrate, fish, bird, amphibian, etc.), synonyms (e.g. lizard, squamata, reptile), and Boolean language (AND, OR). Literature was found indirectly by reviewing relevant articles cited within the original article. Google scholar was also used to examine literature which cited the original as well as those recommended by the database using the “cited by” and “related articles” links, respectively. Many secondary citations were from Herpetological Review, which although indexed by Web of Science, abstracts and full text are not archived or searchable. Therefore, their archive from 1967 to 2019 was downloaded and a comprehensive search of their pdf archives was undertaken. Twitter and ResearchGate was also used to enquire and obtain further citations.

Predatory events were included only if they met the following conditions: (1) an arthropod predator was directly observed attacking and then consuming or attempting to consume a vertebrate, (2) if the prey was not alive it was assumed by the authors to have been caused by the predation event, (3) the event occurred in the field or a natural (not laboratory) experiment (laboratory experiments were thus removed from previous reviews), and (4) the prey was post-hatching (larvae, juveniles, adults). The class, order, and family of the prey and predator, as well as the country where the event occurred was recorded, if available.

A review of all journals referenced was also undertaken on Web of Science to determine what proportion of scientific journals were indexed in a scientific database. An additional literature search was conducted using BioOne to determine the respective bias in the number of published articles between predator and prey groups. All articles between 1965-2020 were searched using key search terms, synonyms, and Boolean language; e.g., (lizard OR gecko OR snake OR Serpentes OR Squamata OR squamate OR testudines OR turtle) was used to search for the number of scientific articles on Squamata. All search terms also included “AND (conservation OR biodiversity OR ecology)” to filter for ecological journals.