New Zealand’s North Island robins (Petroica longipes), known as toutouwai in Maori, are capable of remembering a foraging task taught to them by researchers for up to 22 months in the wild, according to a study published on February 12 in Biology Letters. These results echo the findings of a number of laboratory studies of long-term memory in animals, but offer a rare example of a wild animal retaining a learned behavior with no additional training. The study also has implications for conservation and wildlife management: given the birds’ memory skills, researchers might be able to teach them about novel threats and resources in their constantly changing habitat.
“This is the first study to show [memory] longevity in the wild,” says Vladimir Pravosudov, an animal behavior researcher at the University of Nevada, Reno, who was not involved in the study.
Rachael Shaw, a coauthor and behavioral ecologist at Victoria University in New Zealand, says she was surprised that the birds remembered the new skill she had taught them. “Wild birds have so much that they have to contend with in their daily lives,” she says. “You don’t really expect that it’s worth their while to retain this learned task they hardly had the opportunity to do, and they can’t predict that they will have an opportunity to do again.”
Shaw is generally interested in the cognitive abilities of animals and the evolution of intelligence, and the toutouwai, trainable food caching birds that can live up to roughly 10 years, make perfect subjects for her behavioral investigations. “They’ve got this kind of boldness and curiosity that a lot of island bird species share,” says Shaw. These qualities make them vulnerable to predation by invasive cats, rats, and ermines (also known as stoats), but also inquisitive and relatively unafraid of humans, an ideal disposition for testing memory retention in the field.
In a previous study published in 2017, Shaw demonstrated that wild toutouwai living in the Zealandia Wildlife Sanctuary in Wellington, New Zealand, are capable of learning a novel task. Using a rectangular box with three compartments, each covered by a lid that swivels to the side to reveal its contents, she incrementally taught the birds how to peck the lids aside and retrieve mealworms hidden inside two of the three wells.
Roughly a year later, Shaw was giving a public talk at the sanctuary about conservation and her work with birds. As she explained the memory apparatus she had used in her previous research, a toutouwai appeared.
“I haven’t given this bird this task in over a year,” she recalls telling the audience, “so let’s see how he does.” As if on cue, the bird instantly flew down to the apparatus and started opening the lids. That got her wondering: how many of the other birds could repeat the memory task and how long could they remember what they were taught?
In the new study, Shaw and her coauthor, Annette Harvey, tested 32 of the initial 64 birds that were trained in 2015 and 2016 and banded for individual identification, 30 of which performed the memory task by spontaneously pecking the lids and opening them on their first try. None of the trained birds had seen the box between the initial training and retesting, though some of the untrained control birds had encountered the apparatus in a previous research project. The time between when the birds had first learned the lid-opening behavior and subsequent testing ranged from 10 to 22 months. By contrast, the 17 untrained birds were unable to complete the task.
According to Shaw, the two outliers that didn’t remember the task may have been exceptions to the rule. One of the trained birds was a female that had taken the longest to initially learn the task, and whose dominant male partner interfered with testing. The other bird was old and unwell, and disappeared a few weeks after the experiment.
While Shaw was impressed by her subjects’ performance, Pravosudov says, “I’ve been studying these questions for a long time. It’s not surprising.” Nevertheless, he adds, “it’s good to have more evidence accumulated that the animals are capable of this.” For instance, he cites lab studies that have shown pigeons’ ability to remember and identify photographs and drawings for more than 730 days, and tortoises’ ability to retain an operant conditioning task for nine years. Lab research on Clark’s nutcrackers and chickadees has also found that the birds can remember the locations of hundreds of seeds for six months or more.
“All animals have some basic memories,” he says, “and we may underappreciate how good . . . even [basic] memory is.”
Tim Roth, a behavioral ecologist at Franklin & Marshall College who completed a postdoc with Pravosudov and did not participate in the research, agrees that “we have a lot of information from a lot of different species in a lot of different systems of long-term memory,” including decades of social memory in dolphins and long-term memory in turtles based on one-trial learning. But Roth says he also recognizes the value of studying this particular system of wild birds. “It’s very difficult to get these kinds of opportunistic sorts of observations,” he says, “where you try to do something at one point in time, and then, hopefully, you’ll see the same individuals one or two years later.”
The study found no correlation between forgetting and the amount of time that had lapsed since the birds formed the lid-opening behavior, suggesting that toutouwai may be able to remember the task longer than 22 months. In addition to wanting to test further memory duration, Shaw is interested in investigating whether the birds can recall a more complex piece of information, such as discerning among lids of different colors, which would require them to retain both the lid-opening behavior and the color cue for an extended period of time.
Caroline Strang, a postdoc who studies animal cognition at the University of Texas at Austin and was not involved in the research, says that this study presents an experimental model that could be emulated by other scientists. “This is a population that is being monitored for other purposes,” she says, “and there are lots of populations of birds and other species that have long-term monitoring in the same way. . . . People who are interested in behavior and cognition can go in and capitalize on that by doing more long-term cognition studies.”
Ultimately, Shaw says, she hopes these findings can be used to protect toutouwai in the face of rapid environmental change, and to that end, she is currently developing a protocol to test whether the birds can learn to recognize and avoid cats. “If we can teach them something about the threat of cats before they disperse from the sanctuary,” she says, “and then they can retain that information for a long time, it might really help in boosting their survival outside the fence.”
R.C. Shaw, A. Harvey, “Long-term memory for a learned behavior in a wild bird,” Biology Letters, doi:10.1098/rsbl.2019.0912, 2020.
Amy Schleunes is an intern at The Scientist. Email her at firstname.lastname@example.org.