Adaptive Value

Adaptive value is the way “the observed process contributes to survival [and] if so how survival is promoted and whether it is promoted better by the observed process than by slightly different processes” (Tinbergen, 1963, p. 418). Tool use behavior may emerge in some species and not others due to the differential pressures and adaptive consequences organisms face and engage with on a regular basis. In animals where tool use may enhance foraging or hunting and protection without high cost trade-offs, you might expect to see this behavior.

Sea otters can utilize stones to break open shellfish shells. (Image from Animals.)



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).

Chimpanzees can use a variety of tools to forage. For example, this chimp here is using a stick to forage in a termite mound while termites are abundant during the season. (Image from Discovery News.)

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).

Crocodilian species have recently been discovered to also use tools. Unlike most other tool-using species that use tools for foraging, however, these animals, such as this mugger crocodile, use sticks as traps to lure in birds that are likely to use the sticks for their nests. (Image from Dinets, Brueggen, & Brueggen, 2015, p. 75, Fig. 1.)

Finally, long tailed macaques and California sea otters use rocks to open shellfish (Gumert, Hoong, & Malaivijitnond, 2011; Hall & Schaller, 1964).

This sea otter uses a rock to crack open shells to gain access to the shellfish. (Video from LuisaLMak on YouTube.)

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).

This tool-using crow successfully forages for food in a tree hollow with a stick, which it leaves in the tree hollow for later use by itself or by other birds. (Image from Rutz & St Clair (2011), p. 154, Fig. 1.)

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).

Rooks are capable of using a variety of tools, including hooked sticks to grab distant objects that are inaccessible with their beaks alone. This rook bent a wire to extract a bucket in a tube containing a worm during an experimental session. The images on the right are of wires rooks bent in the experiment. (Image from Bird & Emery (2009), p. 10374, Fig. 6.)



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).

Though octopi are not generally found to be frequent tool users, octopi that find coconut shells have shown the ability to use the shells as shelter against predators.The octopi in this image are shown using the coconuts shells as shelter (top) and "stilt-walking" while carrying the coconut shells (bottom). (Image from Finn, Tregenza, & Norman (2009), p. R1070, Fig. 1.)

Finally, captive Asian elephants have been found to defensively throw logs at other animals (Hart, Hart, McCoy, & Sarath, 2001).