The impact of prolonged frozen storage on the preparation quality of bird skins and skeletons in zoological collections.

Specimens from zoological collections play a pivotal role in improving scientific knowledge in many natural science disciplines. To guarantee an optimum state of conservation and ensure their usefulness, the preparation process employed is crucial. Skins and skeletons are key elements in vertebrate scientific collections and, ideally, are prepared from recently deceased animals; however, specimens are often stored in a frozen state for a long time (years) prior to preparation. Whether the duration of this frozen state has a deleterious effect on preparation quality has rarely been studied. The main objective of this study was thus to contribute towards research into zoological preparation by testing to see whether prolonged frozen storage hinders the preparation of bird skins and skeletons. We used the common buzzard (Buteo buteo) and the barn owl (Tyto alba) as biological models. Our results showed that long-term frozen storage led to weight loss, bone marrow acidification and solidification, and hampered skin preparation. The necropsy affected weight loss and decreased the skin tear resistance, probably due to tissue dehydration. Thus, prolonged frozen storage appears to have a harmful effect on the preparation quality of vertebrate specimens. Since frozen storage could ultimately have an impact on the conservation and scientific use of museum specimens, practices should be implemented to minimise the amount of time specimens are frozen or to mitigate any detrimental effects. More importance should be attached to research on zoological preparation since it is fundamental for optimising the quality, conservation status, and value of museum collections.

Implementing long-term baselines into primate tool-use studies.

Studies on primate tool-use often involve the use of baseline conditions, as they allow for the examination of any differences in the subjects' behavior before and after the introduction of a tool-use task. While these baseline conditions can be powerful for identifying the relative contributions of individual and social learning for the acquisition of tool-use behaviors in naïve (usually captive) subjects, many have criticized them for being too short, and not allowing enough time for the behavior to develop spontaneously. Furthermore, some wild tool-use behaviors such as chimpanzee nut-cracking require animals to manipulate and familiarize themselves with the materials of the behavior within a "sensitive learning period" before it develops later on in life. One solution to this problem is to implement long-term baselines, in which, with collaboration with zoological institutions, the materials of the behavior are left in the enclosure for an extended period. The keepers would then be asked not to demonstrate or train the animals in the target behavior, but to report back to the researchers if they observe the behavior emerge during this extended period. Alongside keeper reports, video cameras could be installed in the enclosure to minimize the chance of false negatives and to allow for coding and inter-rater reliability to be carried out on the videos. These long-term baselines therefore provide extended enrichment opportunities for the animals, alongside allowing the zoological institution to publicize their involvement with the study and guests to observe animals interacting with different testing apparatuses and tools. Finally, long-term baselines can provide invaluable insight on the individual and social learning abilities of primates as well as the potential development stages and sensitive learning periods required for specific behaviors.

An automated aquatic rack system for rearing marine invertebrates.

BACKGROUND: One hundred years ago, marine organisms were the dominant systems for the study of developmental biology. The challenges in rearing these organisms outside of a marine setting ultimately contributed to a shift towards work on a smaller number of so-called model systems. Those animals are typically non-marine organisms with advantages afforded by short life cycles, high fecundity, and relative ease in laboratory culture. However, a full understanding of biodiversity, evolution, and anthropogenic effects on biological systems requires a broader survey of development in the animal kingdom. To this day, marine organisms remain relatively understudied, particularly the members of the Lophotrochozoa (Spiralia), which include well over one third of the metazoan phyla (such as the annelids, mollusks, flatworms) and exhibit a tremendous diversity of body plans and developmental modes. To facilitate studies of this group, we have previously described the development and culture of one lophotrochozoan representative, the slipper snail Crepidula atrasolea, which is easy to rear in recirculating marine aquaria. Lab-based culture and rearing of larger populations of animals remain a general challenge for many marine organisms, particularly for inland laboratories. RESULTS: Here, we describe the development of an automated marine aquatic rack system for the high-density culture of marine species, which is particularly well suited for rearing filter-feeding animals. Based on existing freshwater recirculating aquatic rack systems, our system is specific to the needs of marine organisms and incorporates robust filtration measures to eliminate wastes, reducing the need for regular water changes. In addition, this system incorporates sensors and associated equipment for automated assessment and adjustment of water quality. An automated feeding system permits precise delivery of liquid food (e.g., phytoplankton) throughout the day, mimicking real-life feeding conditions that contribute to increased growth rates and fecundity. CONCLUSION: This automated system makes laboratory culture of marine animals feasible for both large and small research groups, significantly reducing the time, labor, and overall costs needed to rear these organisms.

Looking for Mimicry in a Snake Assemblage Using Deep Learning.

Batesian mimicry is a canonical example of evolution by natural selection, popularized by highly colorful species resembling unrelated models with astonishing precision. However, Batesian mimicry could also occur in inconspicuous species and rely on subtle resemblance. Although potentially widespread, such instances have been rarely investigated, such that the real frequency of Batesian mimicry has remained largely unknown. To fill this gap, we developed a new approach using deep learning to quantify the visual resemblance between putative mimics and models from photographs. We applied this method to Western Palearctic snakes. Potential nonvenomous mimics were revealed by an excess of resemblance to sympatric venomous snakes compared with random expectations. We found that 8% of the nonvenomous species were potential mimics, although they resembled their models imperfectly. This study is the first to quantify the frequency of Batesian mimicry in a whole community of vertebrates, and it shows that even concealed species can act as potential models. Our approach should prove useful for detecting mimicry in other communities, and more generally it highlights the benefits of deep learning for quantitative studies of phenotypic resemblance.

Infrared thermography cannot be used to approximate core body temperature in wild primates.

Understanding the physiological processes that underpin primate performance is key if we are to assess how a primate might respond when navigating new and changing environments. Given the connection between a mammal's ability to thermoregulate and the changing demands of its thermal environment, increasing attention is being devoted to the study of thermoregulatory processes as a means to assess primate performance. Infrared thermography can be used to record the body surface temperatures of free-ranging animals. However, some uncertainty remains as to how these measurements can be used to approximate core body temperature. Here, we use data collected from wild vervet monkeys (Chlorocebus pygerythrus) to examine the relationship between infrared body surface temperature, core body (intra-abdominal) temperature, and local climate, to determine to what extent surface temperatures reflect core body temperature. While we report a positive association between surface and core body temperature-a finding that has previously been used to justify the use of surface temperature measurements as a proxy for core temperature regulation-when we controlled for the effect of the local climate in our analyses, this relationship was no longer observed. That is, body surface temperatures were solely predicted by local climate, and not core body temperatures, suggesting that surface temperatures tell us more about the environment a primate is in, and less about the thermal status of its body core in that environment. Despite the advantages of a noninvasive means to detect and record animal temperatures, infrared thermography alone cannot be used to approximate core body temperature in wild primates.

Is 2020 the year when primatologists should cancel fieldwork?

Year 2020 has brought the greatest global pandemic to hit the world since the end of the First World War. The severe acute respiratory syndrome coronavirus 2 and the resulting disease named coronavirus disease 2019 has brought the world to its knees both financially and medically. The American Society of Primatologists has postponed their annual meetings from the end of May 2020 until the end of September 2020, while the International Primatological Society have postponed their biennial congress from August 2020 to August 2021, which has also resulted in their 2022 meetings in Malaysia being pushed back until 2023. Here, I explore the potential dangers of pursuing any primate fieldwork during this pandemic on our study species, their ecosystems, and local peoples. I believe that the risk of bringing this virus into our study ecosystems is too great and that primatologists should cancel all field research until the pandemic ends or a vaccine/reliable treatment is widely available. This is the year we all must become One Health practitioners!

Eyes in the Sky: Assessing the Feasibility of Low-Cost, Ready-to-Use Unmanned Aerial Vehicles to Monitor Primate Populations Directly.

Primates face many climate and land use change threats, making long-term population monitoring critical to prioritizing conservation efforts. Ground-based line transects are typically conducted to estimate and monitor primate populations. However, transects may be costly and logistically challenging. We sought to test whether low-cost (<5,000 USD), ready-to-use unmanned aerial vehicles (UAVs) could effectively monitor primate populations in north-eastern Madagascar. Critically Endangered [A3cd] golden-crowned sifakas (Propithecus tattersalli) are medium-sized, white lemurs whose creamy colour contrasts against defoliated tree canopies, making them an ideal study species for aerial counts. Quad-copter UAV flights over sifaka groups did not elicit antipredator responses. Photographs demonstrated the ability of UAVs to capture viable imagery of sifakas from approximately 20 m above ground level. Unfortunately, crashes resulting from an inability to programme automated flights over hilly forests cut this pilot study short, highlighting several challenges that remain to implementing UAVs in remote field studies. This study demonstrates that while UAVs offer considerable promise in the future of primate research and conservation, high start-up costs and remote field conditions provide challenging obstacles to first time users hoping to use this exciting new technology. Furthermore, we strongly recommend that thermal cameras be used for direct primate counts with UAVs.

Swimbladder morphology masks Southern Ocean mesopelagic fish biomass.

Within the twilight of the oceanic mesopelagic realm, 200-1000 m below sea level, are potentially vast resources of fish. Collectively, these mesopelagic fishes are the most abundant vertebrates on Earth, and this global fish community plays a vital role in the function of oceanic ecosystems. The biomass of these fishes has recently been estimated using acoustic survey methods, which rely on echosounder-generated signals being reflected from gas-filled swimbladders and detected by transducers on vessels. Here, we use X-ray computed tomography scans to demonstrate that several of the most abundant species of mesopelagic fish in the Southern Ocean lack gas-filled swimbladders. We also show using catch data from survey trawls that the fish community switches from fish possessing gas-filled swimbladders to those lacking swimbladders as latitude increases towards the Antarctic continent. Thus, the acoustic surveys that repeatedly show a decrease in mesopelagic fish biomass towards polar environments systematically overlook a large proportion of fish species that dominate polar seas. Importantly, this includes lanternfish species that are key prey items for top predators in the region, including king penguins and elephant seals. This latitudinal community switch, from gas to non-gas dominance, has considerable implications for acoustic biomass estimation, ecosystem modelling and long-term monitoring of species at risk from climate change and potential exploitation.

Monkey business: Collaborating to grow an ecological physiology of primates.

The lab and field provide differing approaches to studying primate biology. We outline the challenges and benefits of these approaches and demonstrate how collaboration can help bridge these perspectives to provide complementary insight into primate adaptive pathways. With this aim, our collaboration has made tangible insights into the ecological physiology of several primate species, and also yielded more subtle, intangible professional benefits.

A new approach for measuring temperature inside turtle eggs.

For turtles, the thermal environment experienced during development plays critical roles in many biological processes. While the temperature inside an egg is assumed to match the substrate temperature, many factors such as evaporative cooling, metabolic heating and the insulating properties of extra-embryonic components can lead to thermal differences. However, no method developed to date has allowed for measurement of the embryonic temperature in live chelonian eggs. We designed a thermocouple-based technique to measure embryonic temperature, achieving 94% survival in Trachemys scripta This methodology may be applicable to other reptile species. We found that, while the temperature in the substrate adjacent to the eggshell accurately reflects the internal egg temperature, it differs from air temperature (∼2°C) in a moisture-dependent manner. Our results demonstrate that external egg temperature, but not air temperature, is suitable for assessing the effects of temperature on biological processes, which could be critical when considering that processes such as temperature-dependent sex determination in turtles occurs within a 4°C window.

Automated measurement of upper thermal limits in small aquatic animals.

We present a method for automating the measurement of upper thermal limits in small aquatic organisms. Upper thermal limits are frequently defined by the cessation of movement at high temperature, with measurement being performed by manual observation. Consequently, estimates of upper thermal limits may be subject to error and bias, both within and among observers. Our method utilises video-based tracking software to record the movement of individuals when exposed to high, lethal temperatures. We develop an algorithm in the R computing language that can objectively identify the loss of locomotory function from tracking data. Using independent experimental data, we validate our approach by demonstrating the expected response in upper thermal limits to acclimation temperature.

Post-Embryonic Development and Genital-Complex Formation in Three Species of Polyclad Flatworms.

Without the establishment of effective culturing systems, little can be known about the late developmental stages of polyclad flatworms. Here, we report a laboratory culturing system for three polyclad species: Comoplana pusilla, Notocomplana koreana, and Pseudostylochus obscurus, and we describe changes in their morphology from hatching to reproductive maturity. These species hatch out as lobe-less larvae with four eyespots, but the number of eyespots increases in later development. Cross-like and triangularly shaped larvae are observed in N. koreana and P. obscurus, respectively. After settlement, a pale area appears on the body of juveniles and then develops into the copulatory complexes. All three species could be successfully reared on brine shrimp, but only C. pusilla and N. koreana achieved reproductive maturation in such a culturing system. In P. obscurus, switching the food to the gastropod Monodonta labio induced sexual maturation.

Naturalistic path integration of Cataglyphis desert ants on an air-cushioned lightweight spherical treadmill.

Air-cushioned spheres are widely used as treadmills to study behavioural and neurophysiological questions in numerous species. We describe an improved spherical treadmill design that reliably registers the path and walking behaviour of an animal walking on top of the sphere. The simple and robust set-up consists of a very light hollowed styrofoam ball supported by an air stream in a hollow half sphere and can be used indoors and outdoors. Two optical mouse sensors provided with lenses of 4.6 mm focal length detect the motion of the sphere with a temporal resolution of more than 200 frames s-1 and a spatial resolution of less than 0.2 mm. The treadmill can be used in an open- or closed-loop configuration with respect to yaw of the animal. The tethering allows animals to freely adjust their body posture and in the closed-loop configuration to quickly rotate around their yaw axis with their own moment of inertia. In this account, we present the first evidence of naturalistic homing navigation on a spherical treadmill for two species of Cataglyphis desert ants. We were able to evaluate with good precision the walking speed and angular orientation at any time. During homing the ants showed a significant difference in walking speed between the approach and search phases; moreover, they slowed down significantly as soon as they reached zero vector state, the fictive nest position.

Assessing vocal performance in complex birdsong: a novel approach.

BACKGROUND: Vocal performance refers to the ability to produce vocal signals close to physical limits. Such motor skills can be used by conspecifics to assess a signaller's competitive potential. For example it is difficult for birds to produce repeated syllables both rapidly and with a broad frequency bandwidth. Deviation from an upper-bound regression of frequency bandwidth on trill rate has been widely used to assess vocal performance. This approach is, however, only applicable to simple trilled songs, and even then may be affected by differences in syllable complexity. RESULTS: Using skylarks (Alauda arvensis) as a birdsong model with a very complex song structure, we detected another performance trade-off: minimum gap duration between syllables was longer when the frequency ratio between the end of one syllable and the start of the next syllable (inter-syllable frequency shift) was large. This allowed us to apply a novel measure of vocal performance ¿ vocal gap deviation: the deviation from a lower-bound regression of gap duration on inter-syllable frequency shift. We show that skylarks increase vocal performance in an aggressive context suggesting that this trait might serve as a signal for competitive potential. CONCLUSIONS: We suggest using vocal gap deviation in future studies to assess vocal performance in songbird species with complex structure.