Rapid color change in a group-hunting pelagic predator attacking schooling prey.

A major challenge for group-hunting predators is coordinating movement at high speed. Billfish - large predators with an elongated rostrum (bill) - include some of the fastest animals in the ocean and often form groups when hunting. This presents a challenge: how do fast-moving predators wielding dangerous weaponry reliably coordinate their attacks to avoid injury? We report a possible solution to this problem through rapid colour change in group-hunting striped marlin (Kajikia audax) as they hunt schools of Pacific sardines (Sardinops sagax). By analysing high-resolution drone footage of marlin attacks, we found that individual marlin intensified the contrast of their body stripes immediately prior to striking prey schools, before rapidly decreasing intensity after their attack. This suggests that color change may be a reliable signal of motivation to attack, potentially deterring conspecifics from attacking.

Mechanisms of group-hunting in vertebrates.

Group-hunting is ubiquitous across animal taxa and has received considerable attention in the context of its functions. By contrast much less is known about the mechanisms by which grouping predators hunt their prey. This is primarily due to a lack of experimental manipulation alongside logistical difficulties quantifying the behaviour of multiple predators at high spatiotemporal resolution as they search, select, and capture wild prey. However, the use of new remote-sensing technologies and a broadening of the focal taxa beyond apex predators provides researchers with a great opportunity to discern accurately how multiple predators hunt together and not just whether doing so provides hunters with a per capita benefit. We incorporate many ideas from collective behaviour and locomotion throughout this review to make testable predictions for future researchers and pay particular attention to the role that computer simulation can play in a feedback loop with empirical data collection. Our review of the literature showed that the breadth of predator:prey size ratios among the taxa that can be considered to hunt as a group is very large (<100 to >102 ). We therefore synthesised the literature with respect to these predator:prey ratios and found that they promoted different hunting mechanisms. Additionally, these different hunting mechanisms are also related to particular stages of the hunt (search, selection, capture) and thus we structure our review in accordance with these two factors (stage of the hunt and predator:prey size ratio). We identify several novel group-hunting mechanisms which are largely untested, particularly under field conditions, and we also highlight a range of potential study organisms that are amenable to experimental testing of these mechanisms in connection with tracking technology. We believe that a combination of new hypotheses, study systems and methodological approaches should help push the field of group-hunting in new directions.

Two scales of distribution and biomass of Antarctic krill (Euphausia superba) in the eastern sector of the CCAMLR Division 58.4.2 (55°E to 80°E).

Regular monitoring is an important component of the successful management of pelagic animals of interest to commercial fisheries. Here we provide a biomass estimate for Antarctic krill (Euphausia superba) in the eastern sector of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) Division 58.4.2 (55°E to 80°E; area = 775,732 km2) using data collected during an acoustic-trawl survey carried out in February and March 2021. Using acoustic data collected in day-time and trawl data, areal biomass density was estimated as 8.3 gm-2 giving a total areal krill biomass of 6.48 million tonnes, with a 28.9% coefficient of variation (CV). The inaccessibility of the East Antarctic makes fisheries-independent surveys of Antarctic krill expensive and time consuming, so we also assessed the efficacy of extrapolating smaller surveys to a wider area. During the large-scale survey a smaller scale survey (centre coordinates -66.28°S 63.35°E, area = 4,902 km2) was conducted. We examine how representative krill densities from the small-scale (Mawson box) survey were over a latitudinal range by comparing krill densities from the large-scale survey split into latitudinal bands. We found the small scale survey provided a good representation of the statistical distribution of krill densities within its latitudinal band (KS-test, D = 0.048, p-value = 0.98), as well as mean density (t-test p-value = 0.44), but not outside of the band. We recommend further in situ testing of this approach.

Self-organization and information transfer in Antarctic krill swarms.

Antarctic krill swarms are one of the largest known animal aggregations, and yet, despite being the keystone species of the Southern Ocean, little is known about how swarms are formed and maintained. Understanding the local interactions between individuals that provide the basis for these swarms is fundamental to knowing how swarms arise in nature, and what potential factors might lead to their breakdown. Here, we analysed the trajectories of captive, wild-caught krill in 3D to determine individual-level interaction rules and quantify patterns of information flow. Our results demonstrate that krill align with near neighbours and that they regulate both their direction and speed relative to the positions of groupmates. These results suggest that social factors are vital to the formation and maintenance of swarms. Furthermore, krill operate a novel form of collective organization, with measures of information flow and individual movement adjustments expressed most strongly in the vertical dimension, a finding not seen in other swarming species. This research represents a vital step in understanding the fundamentally important swarming behaviour of krill.

Visitor Attitudes Toward Little Penguins (Eudyptula minor) at Two Australian Zoos.

This study identified and compared the attitudes of visitors toward zoo-housed little penguins, their enclosure and visitor experience that may influence the way visitors behave toward little penguins at two Australian zoos. Visitor attitudes were assessed using an anonymous questionnaire, targeting visitor beliefs, and experiences, where visitors were randomly approached at the penguin exhibit after they had finished viewing the penguins. Visitors were given two options to complete the questionnaire, on an iPad during their zoo visit or online (URL sent via email) after their zoo visit. A total of 638 participants (495 at Melbourne Zoo and 143 at Taronga Zoo) completed the questionnaire, 42% were completed onsite during their zoo visit and 58% were completed online after their zoo visit. Most participants were living in Australia, non-zoo members, female, previously or currently owned a pet, aged between 26 and 35 years and had a University degree. Results showed that the attitude dimensions of visitors were consistent between the two zoos which indicates that these measures of attitudes were stable over time and location. Overall, visitors at both zoos had positive attitudes toward little penguins, penguin welfare, the enclosure, and visitor experience. However, whether these positive attitudes and positive visitor experience influenced the way visitors behaved toward the penguins remains unclear. There were some differences in visitor attitudes toward the perceived "aggressiveness" and "timidness" of little penguins, "negative penguin welfare", "experience with the penguins", "learning", "visual barriers" and the way visitors rated their overall experience at the penguin enclosure. While the reasons for the differences in visitor attitudes and visitor experience between the zoos were not clear, some factors such as penguin behavior and enclosure design, may have been attributable to these differences. Also, a relationship was found between visitor attitudes and how visitors rated the welfare of penguins, the enclosure and visitor experience at the enclosure; more positive visitor attitudes were associated with higher ratings of penguin welfare, the enclosure and visitor experience. The practical implications of these results for zoos is unclear because the differences in visitor attitudes were numerically small. This requires further comparisons between zoos or enclosures that are more markedly different than the penguin enclosures in the present study and further research on how visitors assess zoo animals, enclosures and visitor experience.

Effect of Covering a Visitor Viewing Area Window on the Behaviour of Zoo-Housed Little Penguins (Eudyptula minor).

Studies on the effects of visitors on zoo animals have shown mixed findings and as a result, the manner in which visitors affect zoo animals remains unclear for many species, including a rarely studied taxa such as penguins. Penguins are a common zoo-housed species and have been shown to display huddling, vigilance and avoidance towards zoo visitors which can be indicative of fear. Here, we examined the effects of covering one visitor viewing area window, out of four, on little penguin (Eudyptula minor) behaviours that may be indicative of fear. Two treatments were randomly imposed on different days: (1) The main visitor viewing area window, where most visitor-penguin interactions occurred, was uncovered ('Main window uncovered') and (2) The main visitor viewing area window was covered ('Main window covered'). Penguin numbers and behaviour were recorded near the main visitor viewing area window and the three other visitor viewing area windows, as well as one area not visible to visitors ('Corner' area). Furthermore, visitor numbers and visitor behaviour were recorded at all four visitor viewing area windows. Covering the main visitor viewing area window reduced the proportion of visitors present at this window by about 85% (p < 0.001) and reduced potentially threatening visitor behaviours at this window such as tactile contact with the window, loud vocalisations and sudden movement (p < 0.05). When the main visitor viewing area window was covered, the proportion of penguins present increased by about 25% (p < 0.05), the proportion of visible penguins preening in the water increased by about 180% (p < 0.05) and the proportion of visible penguins vigilant decreased by about 70% (p < 0.05) in the area near this main window. A preference for the Corner area was also found whereby 59% and 49% of penguins were present in this area when the main window was uncovered and covered, respectively. These results provide limited evidence that the little penguins in this exhibit showed an aversion to the area near the main visitor viewing area window when it was uncovered based on the increased avoidance and vigilance and decreased preening in the water in this area. This suggests visitors may be fear-provoking for these little penguins. However, it is unclear whether visual contact with visitors per se or other aspects of visitor contact, such as visitor-induced sounds and vibrations, were responsible for this apparent aversion when this window was uncovered.

Dopamine secreting adrenal tumor-ganglioneuroma rather than pheochromocytoma: case report.

Ganglioneuromas are rare, benign, well-differentiated neural crest tumors arising in the paravertebral sympathetic chain, and are classically non-secretory and clinically asymptomatic. As the diagnosis of ganglioneuroma is based on histopathology, the clinical presentation prior to surgical excision often mirrors that of pheochromocytoma or adrenal cortical adenoma. We describe a case of an incidentally found right sided calcified adrenal mass with evidence of marked dopamine excess, suspicious for pheochromocytoma in a 70-year-old female. The patient endorsed a 6-month history of intermittent right flank pain and a 2-year history of weight loss and fatigue. She reported mild symptoms of hypomania but denied other symptoms of dopamine excess including agitation, anxiety, nausea, and vomiting. Exam revealed isolated mild hypertension. The imaging features of this mass were concerning for malignancy including the presence of macrocalcification and irregular borders. After preoperative alpha blockade, the patient underwent open right adrenalectomy and the final pathology was consistent with ganglioneuroma rather than pheochromocytoma. Following resection, the dopamine level normalized, confirming the resected right adrenal ganglioneuroma as the source of dopamine excess. This case represents a rare presentation of dopamine-secreting adrenal ganglioneuroma. This illustrates that although rare, ganglioneuroma should be included on the differential diagnosis for functional adrenal tumors.

Foraging enrichment alleviates oral repetitive behaviors in captive red-tailed black cockatoos (Calyptorhynchus banksii).

The relationship between inadequate foraging opportunities and the expression of oral repetitive behaviors has been well documented in many production animal species. However, this relationship has been less-well examined in zoo-housed animals, particularly avian species. The expression of oral repetitive behavior may embody a frustrated foraging response, and may therefore be alleviated with the provision of foraging enrichment. In this study, we examined the effect of different foraging-based enrichment items on a group of captive red-tailed black cockatoos who were previously observed performing oral repetitive behavior. A group of six cockatoos were presented with five foraging enrichment conditions (no enrichment (control), sliced cucumber, fresh grass, baffle cages, and millet discs). Baseline activity budgets were established over a 10-day preintervention period and interventions were then presented systematically over a 25-day experimental period. This study demonstrated that the provision of foraging interventions effectively increased the median percentage of time spent foraging compared to control conditions (range, 5.0-31.7% across interventions vs. 5.0% for control), with two of the interventions; grass and millet discs, significantly decreasing the expression of oral repetitive behaviors (control = 16.6 vs. 8.3% for both grass and millet discs). Finally, a rapid-scoring method utilized by zookeepers during the study proved to be a useful proxy for the amount of time the cockatoos spent interacting with the foraging interventions and overall time spent foraging.

Curious creatures: a multi-taxa investigation of responses to novelty in a zoo environment.

The personality trait of curiosity has been shown to increase welfare in humans. If this positive welfare effect is also true for non-humans, animals with high levels of curiosity may be able to cope better with stressful situations than their conspecifics. Before discoveries can be made regarding the effect of curiosity on an animal's ability to cope in their environment, a way of measuring curiosity across species in different environments must be created to standardise testing. To determine the suitability of novel objects in testing curiosity, species from different evolutionary backgrounds with sufficient sample sizes were chosen. Barbary sheep (Ammotragus lervia) n = 12, little penguins (Eudyptula minor) n = 10, ringtail lemurs (Lemur catta) n = 8, red tailed black cockatoos (Calyptorhynchus banksia) n = 7, Indian star tortoises (Geochelone elegans) n = 5 and red kangaroos (Macropus rufus) n = 5 were presented with a stationary object, a moving object and a mirror. Having objects with different characteristics increased the likelihood individuals would find at least one motivating. Conspecifics were all assessed simultaneously for time to first orientate towards object (s), latency to make contact (s), frequency of interactions, and total duration of interaction (s). Differences in curiosity were recorded in four of the six species; the Barbary sheep and red tailed black cockatoos did not interact with the novel objects suggesting either a low level of curiosity or that the objects were not motivating for these animals. Variation in curiosity was seen between and within species in terms of which objects they interacted with and how long they spent with the objects. This was determined by the speed in which they interacted, and the duration of interest. By using the measure of curiosity towards novel objects with varying characteristics across a range of zoo species, we can see evidence of evolutionary, husbandry and individual influences on their response. Further work to obtain data on multiple captive populations of a single species using a standardised method could uncover factors that nurture the development of curiosity. In doing so, it would be possible to isolate and modify sub-optimal husbandry practices to improve welfare in the zoo environment.

Consistency of leadership in shoals of mosquitofish (Gambusia holbrooki) in novel and in familiar environments.

In social animal groups, an individual's spatial position is a major determinant of both predation risk and foraging rewards. Additionally, the occupation of positions in the front of moving groups is generally assumed to correlate with the initiation of group movements. However, whether some individuals are predisposed to consistently occupy certain positions and, in some instances, to consistently lead groups over time is as yet unresolved in many species. Using the mosquitofish (Gambusia holbrooki), we examined the consistency of individuals' spatial positions within a moving group over successive trials. We found that certain individuals consistently occupied front positions in moving groups and also that it was typically these individuals that initiated group decisions. The number of individuals involved in leading the group varied according to the amount of information held by group members, with a greater number of changes in leadership in a novel compared to a relatively familiar environment. Finally, our results show that the occupation of lead positions in moving groups was not explained by characteristics such as dominance, size or sex, suggesting that certain individuals are predisposed to leadership roles. This suggests that being a leader or a follower may to some extent be an intrinsic property of the individual.