Foraging Behaviour and Individuality in the Common Wasp (Vespula vulgaris)

<p>The extreme ecological success of insect societies is frequently attributed to the division of labour within their colonies (Chittka & Muller, 2009; Holldobler & Wilson, 2009; E. Wilson & Hölldobler, 2005). Yet, we are far from understanding the causes and consequences of division of labour, implying workers’ specialization (Chittka & Muller, 2009; Dornhaus, 2008). Moreover, little studied is the behaviour of individual workers (Jeanson & Weidenmüller, 2013). Social wasps (Hymenoptera: Vespidae) have received less attention than social bees and ants, and our knowledge of basic aspect of their ecology is still poor (Jeanne, 1991; Greene, 1991). With my thesis, I aimed to contribute to a better understanding of the common wasp (Vespula vulgaris) foraging ecology and organization of labour. With a particular attention to their foraging behaviour, I investigated the inter-individual variability among wasp workers and their cooperation. My thesis shows evidence of information sharing and co-ordination in V. vulgaris foragers’ activity. In fact, the discovery and choice of resources by wasp foragers was assisted by information provided by experienced nestmates (Chapter 2). When resources known to portion of the workforce became newly available, the foraging effort of the whole colony increased. My observations of common wasps are hence consistent with foraging activation mechanisms and suggest piloting (in which one individual leads one or more nestmates to a resource) as a possible foraging recruitment mechanism in social wasps. I found huge variation in lifetime activity, task performance, and survival among common wasp workers (Chapter 3). Some individuals specialized on alternative foraging tasks over their lifetime, and a minority individuals performed a disproportionately high number of foraging trips (elitism). Foragers appeared to become more successful with age, accomplishing more trips and carrying heavier fluid loads. Compared to smaller nestmates, larger wasps contributed more to the colony foraging economies. High mortality was associated with the beginning of the foraging activity, relative to lower mortality in more experienced workers. I evaluated the performance of common wasp workers within the same insect colony, and found empirical support for the hypothesis that specialist foragers are more efficient than generalists (Chapter 4). In fact, V. vulgaris behavioural specialists performed more trips per foraging day and their trips tended to be shorter. Despite their more intense foraging effort, specialists lived longer than generalists. I investigated the intra-colonial variation in the sting extension response (SER) of common wasps, measured as a proxy for individual aggressiveness (Chapter 5). I found that wasps vary greatly in their SER and that individuals change during their life. Aggressive individuals tended to become more docile, while docile individuals more aggressive. Older wasps tended to be more aggressive. Wasp size was not significantly related to the SER. Wasp foragers had a less pronounced sting extension than individuals previously involved in nest defence. For the same individual, the aggressive response was proportional to the intensity of the negative stimulus.</p>

Foraging Behaviour and Individuality in the Common Wasp (Vespula vulgaris)

<p>The extreme ecological success of insect societies is frequently attributed to the division of labour within their colonies (Chittka & Muller, 2009; Holldobler & Wilson, 2009; E. Wilson & Hölldobler, 2005). Yet, we are far from understanding the causes and consequences of division of labour, implying workers’ specialization (Chittka & Muller, 2009; Dornhaus, 2008). Moreover, little studied is the behaviour of individual workers (Jeanson & Weidenmüller, 2013). Social wasps (Hymenoptera: Vespidae) have received less attention than social bees and ants, and our knowledge of basic aspect of their ecology is still poor (Jeanne, 1991; Greene, 1991). With my thesis, I aimed to contribute to a better understanding of the common wasp (Vespula vulgaris) foraging ecology and organization of labour. With a particular attention to their foraging behaviour, I investigated the inter-individual variability among wasp workers and their cooperation. My thesis shows evidence of information sharing and co-ordination in V. vulgaris foragers’ activity. In fact, the discovery and choice of resources by wasp foragers was assisted by information provided by experienced nestmates (Chapter 2). When resources known to portion of the workforce became newly available, the foraging effort of the whole colony increased. My observations of common wasps are hence consistent with foraging activation mechanisms and suggest piloting (in which one individual leads one or more nestmates to a resource) as a possible foraging recruitment mechanism in social wasps. I found huge variation in lifetime activity, task performance, and survival among common wasp workers (Chapter 3). Some individuals specialized on alternative foraging tasks over their lifetime, and a minority individuals performed a disproportionately high number of foraging trips (elitism). Foragers appeared to become more successful with age, accomplishing more trips and carrying heavier fluid loads. Compared to smaller nestmates, larger wasps contributed more to the colony foraging economies. High mortality was associated with the beginning of the foraging activity, relative to lower mortality in more experienced workers. I evaluated the performance of common wasp workers within the same insect colony, and found empirical support for the hypothesis that specialist foragers are more efficient than generalists (Chapter 4). In fact, V. vulgaris behavioural specialists performed more trips per foraging day and their trips tended to be shorter. Despite their more intense foraging effort, specialists lived longer than generalists. I investigated the intra-colonial variation in the sting extension response (SER) of common wasps, measured as a proxy for individual aggressiveness (Chapter 5). I found that wasps vary greatly in their SER and that individuals change during their life. Aggressive individuals tended to become more docile, while docile individuals more aggressive. Older wasps tended to be more aggressive. Wasp size was not significantly related to the SER. Wasp foragers had a less pronounced sting extension than individuals previously involved in nest defence. For the same individual, the aggressive response was proportional to the intensity of the negative stimulus.</p>

Spatial Analysis of Beaked Whale Foraging During Two 12 kHz Multibeam Echosounder Surveys

To add to the growing information about the effect of multibeam echosounder (MBES) operation on marine mammals, a study was conducted to assess the spatial foraging effort of Cuvier’s beaked whales during two MBES surveys conducted in January of 2017 and 2019 off of San Clemente Island, California. The MBES surveys took place on the Southern California Antisubmarine Warfare Range (SOAR), which contains an array of 89 hydrophones covering an area of approximately 1800 km2 over which foraging beaked whales were detected. A spatial autocorrelation analysis of foraging effort was conducted using the Moran’s I (global) and the Getis-Ord Gi∗ (local) statistics, to understand the animals’ spatial use of the entire SOAR, as well as smaller areas, respectively, within the SOAR Before, During, and After the two MBES surveys. In both years, the global Moran’s I statistic suggested significant spatial clustering of foraging events on the SOAR during all analysis periods (Before, During, and After). In addition, a Kruskal-Wallis (comparison) test of both years revealed that the number of foraging events across analysis periods were similar within a given year. In 2017, the local Getis-Ord Gi∗ analysis identified hot spots of foraging activity in the same general area of the SOAR during all analysis periods. This local result, in combination with the global and comparison results of 2017, suggest there was no obvious period-related change detected in foraging effort associated with the 2017 MBES survey at the resolution measurable with the hydrophone array. In 2019, the foraging hot spot area shifted from the southernmost corner of the SOAR Before, to the center During, and was split between the two locations After the MBES survey. Due to the pattern of period-related spatial change identified in 2019, and the lack of change detected in 2017, it was unclear whether the change detected in 2019 was a result of MBES activity or some other environmental factor. Nonetheless, the results strongly suggest that the level of detected foraging during either MBES survey did not change, and most of the foraging effort remained in the historically well-utilized foraging locations of Cuvier’s beaked whales on the SOAR.

Simultaneous GPS-tracking of parents reveals a similar parental investment within pairs, but no immediate co-adjustment on a trip-to-trip basis

Background Parental care benefits the offspring, but comes at a cost for each parent, which in biparental species gives rise to a conflict between partners regarding the within-pair distribution of care. Pair members could avoid exploitation by efficiently keeping track of each other’s efforts and coordinating their efforts. Parents may, therefore, space their presence at the nest, which could also allow for permanent protection of the offspring. Additionally, they may respond to their partner’s previous investment by co-adjusting their efforts on a trip-to-trip basis, resulting in overall similar parental activities within pairs. Methods We investigated the coordination of parental care measured as nest attendance and foraging effort in the Lesser black-backed gull (Larus fuscus), a species with long nest bouts that performs extended foraging trips out of sight of their partner. This was achieved by GPS-tracking both pair members simultaneously during the entire chick rearing period. Results We found that the timing of foraging trips (and hence nest attendance) was coordinated within gull pairs, as individuals left the colony only after their partner had returned. Parents did not match their partner’s investment by actively co-adjusting their foraging efforts on a trip-by-trip basis. Yet, pair members were similar in their temporal and energetic investments during chick rearing. Conclusion Balanced investment levels over a longer time frame suggest that a coordination of effort may not require permanent co-adjustment of the levels of care on a trip-to-trip basis, but may instead rather take place at an earlier stage in the reproductive attempt, or over integrated longer time intervals. Identifying the drivers and underlying processes of coordination will be one of the next necessary steps to fully understand parental cooperation in long-lived species.

Factors affecting the individual foraging behavior in a threatened seabird: Olrog’s Gull (Larus atlanticus) as a case study

The analysis of feeding strategies in animals is one of the most important topics in foraging ecology. The individual’s foraging behavior depends on both the individual’s own actions and the behavior of other foragers. Here we analyse the effect of the sex and group size on the foraging behavior of immature Olrog’s Gull (Larus atlanticus Olrog, 1958), endemic to the Atlantic coast of southern South America and regionally listed a threatened species. Birds were captured, banded, sexed and aged during the non-breeding season in Mar Chiquita coastal lagoon, Argentina. The foraging behavior was quantified by observations made on individuals of known identity, recording the size of foraging groups, as well as prey size and type. Foraging parameters estimated were foraging effort, capture rate and foraging efficiency. Males spent more time in agonistic behavior and captured larger prey. With an increase of group size, the capture rate, the capture of small crabs in males, and foraging effort were higher. The agonistic behaviors, size of consumed prey and foraging effort were affected by individual identity. Our study pinpoints factors underlying variation in the foraging behavior of Olrog’s Gulls and illustrates the importance of modelling individual variation when analyzing foraging behavior.

Physiological adjustments to high foraging effort negatively affect fecundity but not final reproductive output in captive zebra finches

Foraging at elevated rates to provision offspring is thought to be an energetically costly activity and it has been suggested that there are potentially physiological costs associated with the high workload involved. However, for the most part evidence for costs of increased foraging and/or reproductive effort is weak. Furthermore, despite some experimental evidence demonstrating negative effects of increased foraging and parental effort, the physiological mechanisms underlying costs associated with high workload remain poorly understood. To examine how high workload affects hematology, oxidative stress and reproductive output, we experimentally manipulated foraging effort in captive zebra finches, Taeniopygia guttata, using a previously described technique, and allowed individuals to breed first in low foraging effort conditions, and then in high foraging effort conditions. We found that birds up-regulated hematocrit and hemoglobin in response to training. Birds subjected to increased workload during reproduction had lower fecundity, although final reproductive output was not significantly different than that of controls. Offspring of parents subjected to high workload during reproduction also had higher oxidative stress when they were 90 d of age. Total antioxidant capacity and reactive oxygen metabolites of birds responded differently in the two breeding attempts, but we did detect an overall increase in oxidative stress in response to training in either attempt, which could explain the lower fecundity observed in birds subjected to increased workload during reproduction.

Sex-specific energy management strategies in response to training for increased foraging effort prior to reproduction

Free-living animals often engage in behaviour that involve high rates of workload and result in high daily energy expenditure (DEE), such as reproduction. However, the evidence for elevated DEE accompanying reproduction remain equivocal. In fact, many studies have found no difference in DEE between reproducing vs. non-reproducing females. One of the hypotheses explaining the lack of difference is the concept of energetic ceiling. However, it is unclear whether the lack of increases in energy expenditure is due to the existence of an energetic ceiling and/or compensation by males during parental care. To investigate whether an energetic ceiling exists we experimentally manipulated foraging effort in captive zebra finches, Taeniopygia guttata, creating two groups with high- and low foraging effort followed by both groups breeding in a low foraging effort common garden condition. DEE was measured in both sexes throughout the experiment. Our findings showed sex-specific energy management strategies in response to training for increased foraging effort prior to reproduction. Specifically, males and females responded differently to high foraging effort treatment and subsequently to chick rearing in terms of energy expenditure. Our results also suggested that there appears to be an energetic ceiling in females and that energetic costs incurred prior to reproduction can be carried over into subsequent stages of reproduction in a sex-specific manner.