Animal cognition meets ecosystem ecology: the impact of cognition on seed dispersal
Creators: name: Soldati, Francesca
Publisher: name: University of Lincoln
Year: 2023

description: Seed dispersal by endozoochory is important for the maintenance of plantpopulations and biodiversity. As a result, understanding the impact thatfrugivores’ activities have on seed dispersal is essential in order to betterunderstand plant population dynamics. One factor that is known to affect ananimal’s behaviour, yet has received little attention in this context, is animalcognition i.e. whether the information animals learn and remember affects wherethey access fruit and deposit seeds. Therefore, the aim of this thesis was toaddress how animal learning and memory affects the seed dispersal process, usingtwo key approaches – experimental tests of frugivore cognition, and a modelparamaterised to examine the consequences of different cognitive abilities on seeddispersal. Three questions were investigated:(1) The “where?” - whether the ability of frugivores to relocate previouslyvisited food sources impacts upon their movements and, as a consequence, onplants’ seed shadows. The spatial learning and memory of red-footed tortoiseswas tested using an egocentric task. Tortoises were able to navigate efficiently inthe environment, and remembered the spatial location of food for at least twomonths. A seed dispersal model designed to test whether frugivores with differentspatial memory skills differently affect plants’ seed shadow, suggested thatanimals with long spatial memory relocate more efficiently food sources thananimals’ with shorter memory. As a consequence, animals with longer memorysurvived longer, dispersed a bigger amount of seeds, and moved less at randomaround the environment, all of which lead to different spatial distribution ofdeposited seeds.(2) The “What?” - whether seed dispersers’ discriminatory skills andmemory affects their choice of fruit. Tortoises’ ability to discriminate betweenquantity and quality of food was tested. They were able to successfullydiscriminate between the visual cues indicating different types of food andremembered the task for at least 18 months. A seed dispersal model designed to IIinvestigate whether the memory of quality and quantity of food affects seeddispersal showed that the ability to discriminate between the features of fruits and,in particular, the memory of those, allows animals to base their foraging decisionon previous learned experiences, significantly increasing the amount of seeddispersed from the preferred fruit.(3) The “When?” - whether the ability to anticipate events, such as foodavailability, and learn about plants fruiting cycles affects plants’ seed shadows.Tortoises’ anticipatory skills were tested on a 24 h cycle. They were able toanticipate food delivery, showing an increase in activity immediately prior thescheduled food delivery time. A seed dispersal model designed to test the impactof timing on dispersal showed that animals that are able to anticipate cycles equalto or longer than plants’ fruiting cycle readily relocate food, survive longer anddisperse more seeds than those with memory that doesn’t last as long as a fruitingcycle.Finally, I present a model parameterised with red-footed tortoise cognitivedata, with the aim to test one of the characteristics that makes tortoises unusual asseed dispersal vectors: the use of gaps in the forest. The results suggest that theactive use of gaps enhances the probability of seed deposition in gaps anddeforested areas, making tortoises a possible reforestation “tool”.I have demonstrated that the study of frugivores’ cognition can help tobuild more reliable predictions of seed dispersal by endozoochory: cognition isprobably the most effective way to understand and predict an animal’s choicesand movements around the environment. Future research should incorporatecognition in the study seed dispersal via endozoochory to have more reliablepredictions of plant dynamics.