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Cite as: McCune KB, McElreath R, Logan CJ. 2019 Investigating the use of learning mechanisms in a species that is rapidly expanding its geographic range. (version: 11 Oct 2019) In principle recommendation by PCI Ecology.

This preregistration has been pre-study peer reviewed and received an In Principle Recommendation by:

Aliza le Roux (2019) How would variation in environmental predictability affect the use of different learning mechanisms in a social bird? Peer Community in Ecology, 100032. 10.24072/pci.ecology.100032

  • Reviewers: Matthew Petelle and one anonymous reviewer

ABSTRACT

This is one of many studies planned for our long-term research on the role of behavior and learning in rapid geographic range expansions. Project background: Behavioral flexibility, the ability to change behavior when circumstances change based on learning from previous experience (Mikhalevich, Powell, and Logan 2017), is thought to play an important role in a species’ ability to successfully adapt to new environments and expand its geographic range (e.g., (Lefebvre et al. 1997), (Griffin and Guez 2014), (Chow, Lea, and Leaver 2016), (Sol and Lefebvre 2000), (Sol, Timmermans, and Lefebvre 2002), (Sol et al. 2005)). However, behavioral flexibility is rarely directly tested at the individual level, thus limiting our ability to determine how it relates to other traits, which limits the power of predictions about a species’ ability to adapt behavior to new environments. We use great-tailed grackles (a bird species) as a model to investigate this question because they have rapidly expanded their range into North America over the past 140 years ((Wehtje 2003), (Peer 2011)) (see an overview of the 5-year project timeline). Behavioral flexibility was likely necessary for this species to adapt to novel environments during the range expansion. For example, as a tropical species, great-tailed grackles were likely only able to expand through, and persist in, the desert of the southwest United States after humans modified the landscape by building canals and other methods of irrigation (Wehtje (2003)). Although grackles continue to be associated with similarly urban habitats across the range and use human-provided sources of food, one challenge grackles may have to overcome in these novel environments is gaining the ability to recognize and exploit the new stimuli that indicate natural sources of food and water. Similarly, grackles may only be able to survive the harsh winters in the most northern parts of the current range, when invertebrate prey are more scarce, because large sources of grain from cattle feedlots have become more common (Wehtje (2003)). This investigation: The ability to learn individually, or from others, could allow grackles to flexibly change their behavior in response to changing environmental conditions. In this piece of the long-term project, we aim to determine what learning mechanisms grackles use (i.e., stimulus or local enhancement, imitation/emulation, personal information) when learning to solve novel foraging problems. We will use two puzzle box apparatuses that contain food accessible via diverse opening methods. Wild grackles will first be habituated to eating from or off of the non-functional apparatus so that differences in neophobia will not confound performance. We will test grackles from a population in the middle of the expanded geographic range to determine whether this species uses social learning. If so, we will then compare performance across three populations (core, middle of the expansion, and at the northern range edge). Results will indicate how social learning might play a role in the geographic range expansion by elucidating how this species solves novel foraging problems in the wild.

A. STATE OF THE DATA

This preregistration was written (2017) and submitted to Peer Community in Ecology for pre-study peer review (Jul 2019) prior to collecting any data.

B. HYPOTHESES

H1: Information about resources is obtained via individual learning and also transmitted socially in the wild.

Prediction 1: Stimulus enhancement will draw attention to WHAT locus on the apparatus to attend to, and then subjects will rely on personal information to learn HOW to solve that locus. This was found for a similar study on New Caledonian crows (Logan et al. (2016)). We predict that the grackles will behave in the same way because grackles likely need to pay attention to what resources others are accessing, but the exact details of how to access these resources may not be as important because it is likely that most resources are not very complicated to access (e.g., open a sandwich wrapper to eat the sandwich)

P1 alternative 1: Grackles might rely on local enhancement to attend to a particular area and then rely on personal information to explore the area and learn how to solve a particular locus. Grackles may pay more attention to other grackles when determing whether to visit a location to search for food rather than to what specific food might be present in that location.

P1 alternative 2: Individuals may copy (copy partially suggests emulation, or copy completely suggests imitation) the sequence of actions they observed others using to solve a particular locus. This may be a particularly useful mechanism when trying to open complicated packaging (e.g., a plastic ketchup packet). Complicated packaging is likely not as frequently encountered in the wild because easier to access food such as insects might be more abundant.

P1 alternative 3: Individuals do not use social information, but rely solely on personal information when solving novel apparatus loci. This species does not form strong bonds with each other (relative to, for example, monogamous corvids), therefore perhaps social information is not as important to them when solving new problems.

P2: Dominant individuals will solve faster because they can exclude subordinates from accessing the resource. This might also make it appear that males are faster at solving than females because males are reported as being more dominant than females.

P2 alternative 1: Subordinate individuals are more likely to solve the puzzle box faster because they are excluded by dominant individuals from other, easier to access food sources or dominants are able to scrounge from subordinates after they access the food compartments (McCormack, Jablonski, and Brown (2007)).

P3: Older individuals may be better at outcompeting others potentially because they have more experience at solving problems in general. We will be able to test this prediction when comparing juveniles (<1yr) and adults (>1yr), but we will not know the age of the adults unless they were banded as juveniles and became adults by the time the testing occurred. Therefore we will have a limited ability to test this prediction.

P4: It does not require many observations of others attempting to solve or solving at a particular locus to influence which loci observers attempt first. This was found for a similar study on New Caledonian crows (Logan et al. (2016)). We predict that it will be the same for the grackles because grackles likely need to attend to fleeting observations of others as they figure out how to find food in their shared environment. Therefore, there is pressure to attend to any available information.

H2: Performance on the learning task will vary among grackles in the different populations included in this investigation (core, middle of the expansion, and at the range edge).

P5: Individuals from the population on the edge of the grackle range will solve more options faster and rely more on social learning than grackles from the middle of the expanded range, and the original core of the range. This may occur because social information is particularly useful to individuals in novel environments (e.g., the social learning strategy of “copy when uncertain” (Laland 2004)).

P5 alternative 1: Individuals from the population in the core of the grackle range will solve more options faster and rely more on social information than grackles from the middle and the edge of the expanded range. This may occur because the lack of novelty in the endemic range may result in grackles predominantly using individual learning (i.e., producers) which leads to the production of reliable public social information. When social information is consistently high quality, individuals may be selected to preferentially use available social information to navigate unusual novel situations (e.g. social learning strategy of “copy if rare” Laland (2004)).

P5 alternative 2: Individuals from the the middle of the expanded range will solve more options faster and rely more on social information than grackles from the population on the edge of the grackle range, and the original core of the range. This is potentially because population densities might be higher in the middle of the expanded range, therefore there might be more within-species competition for resources such that grackles may be selected to pay increased attention to conspecifics.

P5 alternative 3: There will be no difference in the number of options solved, the speed at which they switch between solving options, and the reliance on personal versus social information on the learning task across grackle populations. This is potentially because grackles in each population are equally social and generalist foragers ((Giraldeau 1996)), measured in a separate preregistration (http://corinalogan.com/Preregistrations/g_flexforaging.html) and rely on a mixture of personal and social information.

H3: Repeated assessments of learning mechanisms with two similar apparatuses will illuminate whether performance is consistent within individuals.

P6: Grackles will show repeatable performance on the learning task over sequential trials with two functionally similar but visually distinct apparatuses (Logan et al. (2016), McCune (2018)). This would indicate that behavioral interactions with the task result from inherent learning abilities.

P6 alternative 1: Grackles will not show repeatable learning performance on the two apparatuses. This could happen for several reasons. First, it may indicate that the two apparatuses may vary in difficulty and so performance on one is not predictive of performance on the other. Second, the distinct visual appearance of the two apparatuses could differentially stimulate behavioral responses that lead to variation in performance (i.e., one apparatus has clear plastic doors therefore the food is visible, while the food is not visible in the other apparatus). Third, grackles may learn to solve the second learning apparatus more quickly after having already learned to solve the first apparatus.