Cross-Species Tool Use
The majority of tool use observed by scientists thus far regards the function of foraging. Dolphins (Allen, Bejder, & Krützen, 2011), orangutans (Fox, Sitompul, & van Schaik, 1999), chimpanzees (Suzuki, Kuroda, & Nishihara, 1995), New Caledonian crows (Rutz & St Clair, 2012), rooks (Bird & Emery, 2009), long-tailed macaques (Gumert, Hoong, & Malaivijitnond, 2011), alligators (Dinets, Brueggen, & Brueggen, 2015),and California sea otters (Hall & Schaller, 1964) are all species that use tools to forage for food.
In each case, available tools differ across ecological niches. It is suspected that dolphins use sea sponges to prod the seafloor in search of prey (Krützen, Mann, Heithaus, Connor, Bejder, & Sherwin, 2005).
Orangutans are found to hammer, poke, probe, and scrape insect mounds as well as fruit (Fox et al., 1999), and, likewise, chimpanzees flexibly use tools from their tool kits to forage for termites in termite mounds based on the seasonality of termite availability (Suzuki et al., 1995).
New Caledonian crows forage for beetle larvae with different kinds of probes (Rutz & St Clair, 2010). Other types of birds, such as rooks and Eurasian jays, use tools in captivity for preferred food items, but are not found to be tool users in the wild (Bird & Emery, 2009; Cheke, Bird, & Clayton, 2011).
Recent research has also suggested that alligators flexibly use tools to lure in prey. An observational study of this species reported that the crocodilians rested sticks on their heads during wading birds’ nesting season but not in the other months of the year (Dinets, Brueggen, & Brueggen, 2015).
Finally, long tailed macaques and California sea otters use rocks to open shellfish (Gumert, Hoong, & Malaivijitnond, 2011; Hall & Schaller, 1964).
The most compelling and scientifically sound example of adaptive value comes from a study on wild New Caledonian crows that demonstrated the nutritional content of beetle larvae, which are only obtainable by using tools, was higher than the nutritional content found in more easily obtained food items (Rutz & St Clair, 2010). As such, the crows that use tools to capture these beetle larvae will have better nutritional profiles than their counterparts that are not using tools to reach this food source, putting the tool-using crows at an advantage (Rutz & St Clair, 2010).
In rooks and Eurasian jays, tool use is only observed in captive animals when they are in a situation in which it would be more beneficial to use tools to forage than to not use tools at all (Bird & Emery, 2009; Cheke et al., 2011). This suggests that in the wild it is more costly to expend energy on tool use behavior, as the organism then needs to learn how to manipulate the tool accurately to achieve a desired outcome, when the organism could instead be expending less energy by relying on morphological adaptations (Bird & Emery, 2009; Cheke et al., 2011).
Another facet of the adaptive value of tool use is protection. In addition to using sponges to enhance foraging, this behavior shields dolphins’ rostrums from becoming harmed by stray rocks or crustaceans while pushing up sand from the seafloor (Krützen et al., 2005).
Octopi, another ocean-dwelling animal collect and use coconut shells to shield themselves from predators (Finn, Tregenza, & Norman, 2009).
Finally, captive Asian elephants have been found to defensively throw logs at other animals (Hart, Hart, McCoy, & Sarath, 2001).