abstract: Social animals benefit from the aggregation of knowledge and cognitive processing power. Part of this benefit comes from individual heterogeneity, which provides the basis to group-level strategies, such as division of labor and collective intelligence. In turn, the outcomes of collective choices, as well as the needs of the society at large, influence the behavior of individuals within it. My dissertation research addresses how the feedback between individual and group-level behavior affects individuals and promotes collective change. I study this question in the context of seed selection in the seed harvester ant, Pogonomyrmex californicus. I use both field and laboratory studies to explore questions relating to individual behavior: how forager decision-making is affected through information available in the nest and at the seed pile; how workers interact with seeds in the nest; and how forager preferences diverge from each other’s and the colony’s preference. I also explore the integration between individual and colony behavior, specifically: how interactions between the foraging and processing tasks affect colony collection behavior; how individual behavior changes affect colony preference changes and whether colony preference changes can be considered learning behavior. To answer these questions, I provided colonies with binary choices between seeds of unequal or similar quality, and measured individual, task group, and colony-level behavior. I found that colonies are capable of learning to discriminate between seeds, and learned information lasts at least one month without seed interaction outside of the nest. I also found that colony learning was coordinated by foragers receiving updated information from seeds in the nest to better discriminate and make choices between seed quality during searches for seeds outside of the nest. My results show that seed processing is essential for stimulating collection of novel seeds, and that foraging and processing are conducted by behaviorally and spatially overlapping but distinct groups of workers. Finally, I found that foragers’ preferences are diverse yet flexible, even when colonies are consistent in their preference at the population level. These combined experiments generate a more detailed and complete understanding of the mechanisms behind the flexibility of collective colony choices, how colonies incorporate new information, and how workers individually and collectively make foraging decisions for the colony in a decentralized manner. / Dissertation/Thesis / Doctoral Dissertation Biology 2020

Advances in Down syndrome (DS) research depend on the availability of mouse models that replicate the genetic landscape and resulting phenotypes of DS which allow for experimental manipulation to correlate cellular and molecular changes with behavior, in a way that is not possible with human studies alone. These models have been a critical component in understanding the underlying mechanism of the intellectual disability in people with Down syndrome. The Ts(1716)65Dn (Ts65Dn) mouse is one of the most commonly used models as it recapitulates many of the phenotypes seen in individuals with Down syndrome, including neuroanatomical changes and impaired learning and memory. Although Ts65Dn exhibits a number of traits also present in DS, studies have produced variable results across time that call into question the validity of Ts65Dn and its use as a tool for studying Down syndrome. As Ts65Dn is the platform employed to gather preclinical evidence for treatments of DS, a critical assessment regarding the validity of the model over time is necessary. In this study, we conduct a rigorous and comprehensive, comparative analysis of multiple cohorts from the Ts65Dn line to assess the stability and reproducibility of neuroanatomical and behavioral characteristics. We measured gross anatomical brain and body size, neuronal density in the hippocampus and cerebellum, alterations to oligodendrocyte maturation and myelination, acquisition of developmental milestones, and learning and memory performance using the Morris water maze. Our results show a significant amount of variability in Ts65Dn, both across as well as within cohorts. Inconsistent phenotypes in Ts65Dn mice highlight specific cautions and caveats for use of these mice when studying Down syndrome and suggest it is not always the most appropriate model system to use. In addition to phenotypic variability, a major pitfall of the Ts65Dn model is the unintended triplication of 60 non-DS-related genes and the unknown consequences on resulting phenotypes. Recent advances in gene editing strategies have allowed for the gene dosage normalization of those 60 genes and the generation of a new mouse model of Down syndrome, Ts66YAH. As this newly developed line has not yet been characterized, we conducted an analysis complimentary to our study of Ts65Dn to investigate the utility of Ts66YAH for Down syndrome research. We found Ts66YAH mice show no measurable neuroanatomical changes, developmental delays, or learning and memory deficits suggesting that the deleted non-DS-related genes do influence the phenotypes seen in Ts65Dn. Although Ts66YAH is a more genetically representative model of Down syndrome compared to Ts65Dn, it does not exhibit disease relevant phenotypes and therefore, may not be a suitable model for studying DS. The various downfalls identified in the present study may be impacting other mouse models of DS as well and thus, our analysis of Ts65Dn across time and comparative study of Ts66YAH illustrate the need for careful use and increased rigor to ensure translational and reproducible results when working with all mouse models of Down syndrome.

Several studies have investigated the ecological factors that affect behavior in Micrathena gracilis, a diurnal orb-weaving spider that forages on flying insects during the day. However, none yet have considered how the temporal distributions of prey and predator occurrences shape their daily behavioral rhythms, especially web construction, which involves a heavy energetic investment well in advance of potential nutritional benefit. Recently, several orb-weaving spider species have been shown to exhibit a variety of abnormal rhythms, suggesting that circadian clock-controlled rhythms may play an unexpected role in behavioral evolution. Despite the appearance of significant insect abundance in the evenings, M. gracilis individuals stop foraging, take down their webs, and retreat before they can capitalize on this opportunity. Is the nutritional benefit of this forfeited prey significant compared to what they collect during the day, and if so, what potential cost might justify opting out of this potential gain? To investigate, sticky traps for prey collection and a camera array for recording predator activity were used at a local field site to survey what risks and rewards these spiders face throughout the 24-hour day. Spider activity and web captures in the field were also used to confirm behavioral patterns and capture success throughout the day. It was found that spiders begin foraging when prey becomes available but cease while prey is still abundant. These observations appear to support a theoretical model of behavioral decisions under predation risk. However, recorded predation events were rare, and predation was not confirmed outside of the foraging timeframe. These results support the notion that the circadian rhythm of Micrathena gracilis is shaped by factors other than prey availability, but the theoretical pressure from predation risk requires further investigation.

Play is a behavior mainly observed in young individuals that can differ greatly between species in both function and appearance. Presence of play indicates positive experiences in animals, making play a useful assessment tool for animal welfare. Commercial hatcheries expose chicks to several stressors that can affect both behavior and welfare. Unfortunately, our understanding of play behavior in chickens is still limited as only a few studies have been conducted.Therefore, the aim of this study was to describe the ontogeny of various play behaviors in modern laying hens and to investigate how stress affects play behavior in chicks. A total of 80 chicks were used whereas 40 were hatched at a hatchery and 40 were hatched under controlled conditions. The chicks were tested in groups of four in enriched test arenas twice a week during five weeks. Each test lasted 30 minutes and novel objects were placed inside the arena after 10 and 20 minutes. Behaviors were noted while analyzing videos from the experiment using one–zero sampling and later divided into the categories of solitary, social, and total play. A linear mixed model with repeated measures was used to investigate how treatment, age, and the interaction treatment*age affect play behavior. Chicks played more during certain ages and all forms of play showed a similar change with age over both treatments. The amount of play did not differ significantly between treatments but there was a numerical (non-significant) tendency for hatchery chicks to play more, which may indicate compensatory play.

<p>Green turtles (<em>Chelonia mydas</em>) perform ocean-crossing migrations, maintain healthy marine ecosystems, generate income through tourism, and are endangered and declining globally. For these reasons, among others, this species has been a focus of numerous research programs worldwide for almost a century. Most of these sea turtle research programs require some form of animal handling to collect the required data (e.g., tagging information or the collection of biological samples). However, this can cause stress, especially for wild animals, and that raises ethical issues. Here, I describe novel methods for assessing and mitigating the effects of handling stress on green turtles. Specifically: (1) I used a combination of animal-borne cameras and drone footage to determine how handling stress altered the post-release behavior of green turtles and (2) I used a photo-ID software to determine whether flipper scales can provide more accurate identifications than the more conventionally used facial scale patterns. </p> <p><br></p> <p>I found that turtles spent more time swimming and had shortened dive intervals in the first 30 mins after capture and attachment of a camera than in the hours that follow. Instances of socializing, foraging and resting increased over the 3-3.5 h after release. Animals recorded by drone and not captured were less likely to rest, which suggests this behavior may be a recovery response to handling and/or stress. The same animals were also more likely to socialize. When determining the accuracy of flipper or facial images for photo-ID, I found that head scales provided correct identifications 80% of the time, whereas the flipper provided correct identifications 100% of the time. This implies that researchers could use the flipper instead of more invasive tagging techniques, such as metal flipper tags or using lights to photograph the face for photo-ID, which can induce stress.</p>

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In the early twentieth century, Karl von Frisch performed seminal work on the organization of social behavior of honey bees. Much of his work involved training individual foragers to distant artificial feeders. Similar training methods have been used in research laboratories for the better part of a century, and these methods lend themselves well to advanced undergraduate biology classes in animal behavior. In recent years, students have used these methods in group projects to study color preference and time-memory. In this Technical Paper, we describe the basic steps of training honey bees to a distant feeder. We also provide alternative methods for answering specific types of questions that students in animal behavior classes might wish to address.