Laura Marina Biondi

Inter-individual and age differences in exploration, neophobia and problem-solving ability in a Neotropical raptor ( Milvago chimango )

Animal innovations have far-reaching ecological and evolutionary consequences. The occurrence and persistence of an innovation require several processes, including exploration, social and asocial learning, and low neophobia. In addition, the identity of the innovator may determine how these new behaviours are socially transmitted. Taking into account inter-individual and age differences, we investigated three correlates of animal innovation: object exploration, neophobia level and novel problem-solving ability in an opportunistic generalist raptor, the Chimango Caracara (Milvago chimango). Eighteen individuals (7 adults and 11 juveniles) were caught during the non-breeding period and housed in individual cages in outdoor aviaries. Each bird was given three tests: exploration, neophobia and problem-solving. Individuals differed in their response to novel situations both within and between age groups. Most of the juveniles were more explorative and had a lower neophobic response to a strange object than adult birds, but both age groups were able to solve a novel problem when given a food reward. In juveniles, neophobia level and problem-solving performance were inversely related; however, we found no relationship between these behaviours in adults. Exploration did not correlate with neophobia or problem-solving ability for either age group. This research is one of the few studies exploring the inter-individual and age differences in behavioural innovation and their correlates in a bird of prey. The explorative tendency, low neophobia and ability to innovate showed by M. chimango may be advantageous for this generalist and opportunistic raptor and might be some of the factors underlying its ecological success.

Experimental assessment of problem solving by Milvago chimango (Aves: Falconiformes)

We report a preliminary assessment of problem solving as an estimate of behavioural innovation and learning ability of a generalist and abundant raptor, Milvago chimango, under controlled conditions in aviaries. Experimental tests consisted in presentation of a Plexiglas box with four lids leading to isolated pieces of meat. We recorded time to first contact with the box and time from this first contact to gaining access to the pieces of meat. We recorded the number of attempts to open the box and reach the first portion of meat, and the total number of lids opened by each individual during five successive daily sessions. We found that individuals of M. chimango quickly approached and made contact with the Plexiglas box, and responded successfully to the novel feeding problem of reaching the food inside. In our study, performance of individuals was enhanced after solution of the novel task for the first time, as indicated by the progressively reduced time taken to access the food. Further, some individuals gained access to an increasing number of sections of the Plexiglas box during subsequent sessions, suggesting significant learning ability. Our results indicated M. chimango has a remarkable ability to obtain food in a novel situation, an observation that agrees with anecdotal reports of opening of receptacles to obtain food in urban environments. The results support the idea of behavioural plasticity in this species.

Neophobia is negatively related to reversal learning ability in females of a generalist bird of prey, the Chimango Caracara, Milvago chimango

In an ever-changing environment, the ability to adapt choices to new conditions is essential for daily living and ultimately, for survival. Behavioural flexibility allows animals to maximise survival and reproduction in novel settings by adjusting their behaviour based on specific information and feedback acquired in their current environments. However, a growing body of evidence indicates that an individual’s personality type can limit the extent to which the individual might behave flexibly, by influencing the way an individual pays attention to novelty and how much information it collects and stores, which in turn affects the individual’s decision-making and learning process. In this study, the behavioural flexibility of a generalist predator, the Chimango Caracara, Milvago chimango, was analysed using the reversal learning paradigm, focusing on the comparison between age classes, and the relation of learning flexibility with a personality trait, the level of neophobia. Due to the low number of male individuals captured, this study was carried out only with female birds. The results showed that age had no significant effect either on the acquisition of a stimulus-reward association, or on the capacity of reversing this previously learned association. Reversal of the response was a harder task for these birds in comparison with the initial acquisition process. The individual’s performances in the learning tasks seemed to be uncorrelated with each other, suggesting that they involve different neural mechanisms. Contrary to the general pattern observed in the majority of previous work on personality and cognition in non-human animals, the level of neophobia did not correlate with the initial associative learning performance in both adults and juveniles, yet it showed a significant negative relationship with reversal learning ability, mainly in the regressive phase of this task, for the two age classes. Our results suggest that the predatory and generalist lifestyle of female individuals of M. chimango along with the selective pressures of the environment of the individuals studied might play a critical role in the degree and direction of the linkage between novelty response and learning flexibility observed in this study.

The role of stimulus complexity, age and experience in the expression of exploratory behaviour in the Chimango Caracara, Milvago chimango

Exploration represents an important way by which organisms evaluate environment information. The decision of whether or not an animal should investigate environmental changes may influence the extent to which animals learn about their surroundings and cope with habitat modifications. We analysed exploration behaviour in a suburban population of a raptor species, the Chimango Caracara, Milvago chimango, by examining how age, previous experience and object complexity influence novel object exploration. Our findings showed that object complexity did not influence caracaras initial approach and contact with objects, but did influence the degree of engagement during exploratory activities, as measured by total exploration time and number of exploration events. These variables were higher for complex objects than for simple objects. Experience resulted in less exploration of simple objects. It is likely that, for caracaras, simple objects are easier to encode and recall than complex objects, so additional exploration of such objects would not provide further information. Results suggest that exploratory behaviour in this raptor was guided more by the benefits of a greater quantity of information obtained by exploring complex objects, than by the risks associated to this activity. We can conclude that caracaras cope with novel features in their surroundings with a novelty-seeking strategy, characteristic for generalist species in discovering early new resources opportunities, and which might be a determining factor for adaptive responses to environment modification.

Red-Backed Hawks Supply Food to Scavenging Chimango Caracaras

Abstract Positive interactions between species of terrestrial vertebrates occur frequently and it is common among birds. However, such interactions have generally been overlooked in raptor field studies. We analysed interactions between Red-backed Hawks (Buteo polyosoma) and Chimango Caracaras (Milvago chimango) in order to determine the characteristics of the association between these two South American raptors. We observed 171 bouts of activity, 40 when Red-backed Hawks were feeding and 131 when the Hawks were undertaking other activities. Chimango Caracaras were more often present when Red-backed Hawks were feeding (81%) than during other activities of Red-backed Hawks (69%), but they attacked Red-backed Hawks more frequently during other activities of the Hawks (66%) than when the Hawks were feeding (43%). In addition, the rate of attacks by Chimango Caracaras was higher during other activities of the Hawks (mean = 2.21 attacks per Caracara) than when the Hawks were feeding (mean = 0.68 attacks per Caracara). Duration of feeding activities was not affected significantly by the presence of Chimango Caracaras or by attacks by the Caracaras. During 16 of 40 feedingbouts of Hawks, an average of 1.81 ± 0.23 (s.e.) Caracaras fed on prey discarded by the Hawks. Thus, Red-backed Hawks indirectly supplied food to Chimango Caracaras, which, in turn, reduced their agonistic behaviour towards Hawks. Our findings represent one of few cases reported about facilitative associations among raptors, but it seems likely that it represents a common strategy among these birds.

Postnatal development of subterranean habits in tuco-tucos Ctenomys talarum (Rodentia, Caviomorpha, Ctenomyidae)

Postnatal development of subterranean habits was investigated in Los Talas’ tuco-tuco Ctenomys talarum, a subterranean caviomorph rodent endemic from South America. Since in this species, some key morpho-functional traits related to scratch-digging behaviour—a form of underground progression—are already present during early ontogeny and develop progressively, we predicted that this behaviour expresses early during postanatal development and its performance enhances gradually from pups to adults. The process of acquisition of different behaviours associated to the construction of a burrow system was recorded in 11 individuals, each one coming from different litters, inside a terrarium filled with natural soil. We found that scratch-digging and burrowing behaviours expressed early during postnatal development, particularly, during lactancy. The digging of a “true burrow” clearly preceded the dispersal age, with a high inter-individual variability, from 18 (lactancy) to 47 (post-weaning) postnatal days. Pups could lose the soil using their foreclaws and remove the accumulated substrate using their hindfeet as adults do. During lactancy individuals could construct a simple burrow to shelter, and first burrow construction occurred in the absence of either a burrowing demonstrator or an early subterranean environment (a natal burrow). However, certain features of the complex burrow system that characterize this species, such as lateral branches and nest chamber, just appeared after weaning. The time elapsed until animals started to dig and the time dedicated to underground activities varied with age, decreasing and increasing, respectively. In sum, our results show that—in C. talarum—immature digging behaviour gets expressed early during ontogeny, and develops progressively. The role of the early ability to build its own burrow and its possible function influencing the development of musculoskeletal traits and on efficiency for such conduct is discussed.

Diversidad de Tetrápodos en un mosaico de ambientes del sudeste de la ecorregión Pampeana como herramienta para planificar en conservación

A pesar del avance en el conocimiento de la biodiversidad para ciertas regiones, este se encuentra en general disperso y no ha sido interpretado respecto a sus propiedades emergentes ni puesto en contextos que faciliten la toma de decisiones en conservacion. El sudeste de la ecorregion Pampas presenta una diversidad ambiental destacada en un area relativamente restringida, y existe ademas una importante cantidad de informacion sobre diversidad de Tetrapodos. Nuestro objetivo fue compilar y analizar este cumulo de informacion, a traves de una lista de especies con sus abundancias relativas por ambientes destacando aquellas endemicas y de interes para la conservacion. Evaluamos la complementariedad entre los taxa (anfibios, reptiles, aves y mamiferos) en terminos de composicion, numero de especies totales y amenazadas. La diversidad de Tetrapodos recopilada pone de manifiesto que esta pequena area presenta una importante riqueza de especies (12 especies de anfibios, 26 reptiles, 233 aves, 34 mamiferos; 41 estan amenazadas y tres son endemicas). Los ambientes representados (pastizales, dunas, sierras, humedales, estuarios, marino, agroecosistemas, urbanizaciones) contribuyen diferencialmente a la diversidad general de Tetrapodos. La distribucion desproporcionada de la riqueza de especies, de especies amenazadas y de la composicion entre ambientes dentro de cada taxon, entre taxa y entre diferentes unidades ambientales destacan la utilidad de este tipo de analisis en la interpretacion de la variacion espacial de la biodiversidad y deberian contribuir en la planificacion territorial en un marco que optimice la conservacion.