Estudio del movimiento de poblaciones animales: redes complejas de interaccin inspiradas en datos de campo / Study of animal population movement: complex interaction networks inspired by field data

Madile Hjelt, Marco (2023) Estudio del movimiento de poblaciones animales: redes complejas de interaccin inspiradas en datos de campo / Study of animal population movement: complex interaction networks inspired by field data. Master in Physical Sciences, Universidad Nacional de Cuyo, Instituto Balseiro.

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Abstract in Spanish

A pesar de ser una de las especies ms comercializadas en el mercado ilegal de mascotas de Argentina, se conoce muy poco sobre la tortuga terrestre Chelonoidis chilensis en su hbitat natural. Debido a la creciente fragmentacin de su hbitat producida principalmente por la reciente introduccin de ganado, esta tortuga est catalogada como especie en estado vulnerable. Por estos motivos resulta muy importante el estudio de sus refugios, su rea de movimiento y las relaciones entre las tortugas dentro de la comunidad. La poblacin de estudio se encuentra en el lmite sur de su distribucin geogrfica, en las cercanas de San Antonio Oeste, Patagonia, Argentina. Por ser reptiles se los considera solitarios, aunque se sabe muy poco sobre su red de interaccin social. En este trabajo, seis individuos de Chelonoidis chilensis fueron monitoreados continuamente durante sus diferentes perodos de actividad, utilizando un dispositivo GPS autnomo. Se implement un mtodo de filtrado de trayectorias y se construy una grilla de zonas de inters para las tortugas, utilizando las trayectorias filtradas. Se estudiaron las interacciones diurnas, armando redes de encuentros entre tortugas y se encontr el mximo de densidad de red de encuentros en el perodo asociado al apareamiento, disminuyendo a cero para el perodo de brumacin. Curiosamente, las interacciones entre machos se encontraron ms probables durante el perodo de apareamiento, lo que podra estar relacionado con la observacin de peleas frecuentes durante este perodo. Realizando simulaciones numricas usando pasos y tamaos de campo observados, concluimos que las densidades de la red de encuentros diurnos son mucho ms altas que las observadas por casualidad. Esto aade evidencia a la presencia de comportamiento social dentro de este reptil vulnerable. Para muchas especies, los refugios son un recurso esencial para la proteccin de depredadores y las extremas condiciones ambientales. Los refugios tambin pueden servir para interacciones sociales como el apareamiento. Por lo tanto, el conocimiento de los patrones de uso de refugios puede proporcionar informacin sobre la estructura social. En este trabajo, se implement un criterio para identificar los refugios nocturnos de las tortugas. Sobre estos se calcul la distancia media entre refugios y su centro de masa, tanto para machos como para hembras y no se encontraron diferencias significativas en el rea abarcada por los refugios para ambos sexos. Se armaron redes bipartitas de nodos tortuga y refugio, y se encontr que la tortuga comparte menos refugios y utiliza una menor cantidad diferente de los mismos en cuanto se acerca el perodo de brumacin. Este hecho puede ser importante al considerar la eventual propagacin de enfermedades. Finalmente, se descubri la existencia de refugios preferidos y que la tortuga utiliza refugios cercanos entre s respecto a los dems refugios de la poblacin.

Abstract in English

Despite being one of the most traded species in the illegal pet market in Argentina, very little is known about the land turtle Chelonoidis chilensis in its natural habitat. Due to the increasing fragmentation of its habitat caused mainly by the recent introduction of livestock, this turtle is listed as a vulnerable species. For these reasons, the study of their burrows, their area of movement, and the relationships between turtles within the community is very important. The study population is located at the southern limit of its geographical distribution, near San Antonio Oeste, Patagonia, Argentina. Being reptiles, they are considered solitary, although very little is known about their social interaction network. In this work, six individuals of Chelonoidis chilensis were continuously monitored during their different periods of activity, using an autonomous GPS device. A method of trajectory filtering was implemented and a grid of zones of interest for the turtles was constructed, using the filtered trajectories. Daytime interactions were studied, assembling networks of encounters between turtles and the maximum density of the encounter network was found in the period associated with mating, decreasing to zero for the brumation period. Interestingly, interactions between males were found more likely during the mating period, which could be related to the observation of frequent fights during this period. Conducting numerical simulations using observed steps and field sizes, we concluded that the densities of the daytime encounter network are much higher than those observed by chance. This adds evidence to the presence of social behavior within this vulnerable reptile. For many species, burrows are an essential resource for protection from predators and extreme environmental conditions. Burrows can also serve for social interactions such as mating. Therefore, knowledge of burrow usage patterns can provide information about social structure. In this work, a criterion for identifying the turtles’ nocturnal burrows was implemented. On these, the average distance between burrows and their center of mass was calculated, both for males and females, and no significant differences were found in the area covered by the burrows for both sexes. Bipartite networks of turtle and burrow nodes were constructed, and it was found that the turtle shares fewer burrows and uses a smaller different number of them as the brumation period approaches. This fact may be important when considering the eventual spread of diseases. Finally, the existence of preferred burrows was discovered and that the turtle uses burrows close to each other compared to other burrows in the population.

Item Type:Thesis (Master in Physical Sciences)
Keywords:[Complex networks; Redes complejas; Chelonoidis chilensis; Tortuga terrestre argentina; Burrow usage; Madriguera; Animal movement; Movimiento animal; Trajectory analysis; Anlisis de trayectorias]
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Subjects:Physics > Sistemas complejos
Divisions:Gcia. de rea de Investigacin y aplicaciones no nucleares > Gcia. de Fsica > Sistemas complejos y altas energas > Fsica estadstica interdisciplinaria
ID Code:1239
Deposited By:Marisa G. Velazco Aldao
Deposited On:30 Apr 2024 11:56
Last Modified:30 Apr 2024 12:01

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