Minimizing observer bias in behavioral research: blinded methods reporting requirements for Behavioral Ecology and Sociobiology

The effects of ocean acidification on fishes - history and future outlook

The effects of increased levels of carbon dioxide (CO2 ) on the Earth's temperature have been known since the end of the 19th century. It was long believed that the oceans' buffering capacity would counteract any effects of dissolved CO2 in marine environments, but during recent decades, many studies have reported detrimental effects of ocean acidification on aquatic organisms. The most prominent effects can be found within the field of behavioural ecology, e.g., complete reversal of predator avoidance behaviour in CO2 -exposed coral reef fish. Some of the studies have been very influential, receiving hundreds of citations over recent years. The results have also been conveyed to policymakers and publicized in prominent media outlets for the general public. Those extreme effects of ocean acidification on fish behaviour have, however, spurred controversy, given that more than a century of research suggests that there are few or no negative effects of elevated CO2 on fish physiology. This is due to sophisticated acid-base regulatory mechanisms that should enable their resilience to near-future increases in CO2 . In addition, an extreme "decline effect" has recently been shown in the literature regarding ocean acidification and fish behaviour, and independent research groups have been unable to replicate some of the most profound effects. Here, the author presents a brief historical overview on the effects of elevated CO2 and ocean acidification on fishes. This historical recap is warranted because earlier work, prior to a recent (c. 10 year) explosion in interest, is often overlooked in today's ocean acidification studies, despite its value to the field. Based on the historical data and the current knowledge status, the author suggests future strategies with the aim to improve research rigour and clarify the understanding of the effects of ocean acidification on fishes.

Meta-analysis reveals an extreme "decline effect" in the impacts of ocean acidification on fish behavior

Ocean acidification-decreasing oceanic pH resulting from the uptake of excess atmospheric CO2-has the potential to affect marine life in the future. Among the possible consequences, a series of studies on coral reef fish suggested that the direct effects of acidification on fish behavior may be extreme and have broad ecological ramifications. Recent studies documenting a lack of effect of experimental ocean acidification on fish behavior, however, call this prediction into question. Indeed, the phenomenon of decreasing effect sizes over time is not uncommon and is typically referred to as the "decline effect." Here, we explore the consistency and robustness of scientific evidence over the past decade regarding direct effects of ocean acidification on fish behavior. Using a systematic review and meta-analysis of 91 studies empirically testing effects of ocean acidification on fish behavior, we provide quantitative evidence that the research to date on this topic is characterized by a decline effect, where large effects in initial studies have all but disappeared in subsequent studies over a decade. The decline effect in this field cannot be explained by 3 likely biological explanations, including increasing proportions of studies examining (1) cold-water species; (2) nonolfactory-associated behaviors; and (3) nonlarval life stages. Furthermore, the vast majority of studies with large effect sizes in this field tend to be characterized by low sample sizes, yet are published in high-impact journals and have a disproportionate influence on the field in terms of citations. We contend that ocean acidification has a negligible direct impact on fish behavior, and we advocate for improved approaches to minimize the potential for a decline effect in future avenues of research.

Meta-analysis reveals an extreme "decline effect" in the impacts of ocean acidification on fish behavior

Ocean acidification-decreasing oceanic pH resulting from the uptake of excess atmospheric CO2-has the potential to affect marine life in the future. Among the possible consequences, a series of studies on coral reef fish suggested that the direct effects of acidification on fish behavior may be extreme and have broad ecological ramifications. Recent studies documenting a lack of effect of experimental ocean acidification on fish behavior, however, call this prediction into question. Indeed, the phenomenon of decreasing effect sizes over time is not uncommon and is typically referred to as the "decline effect." Here, we explore the consistency and robustness of scientific evidence over the past decade regarding direct effects of ocean acidification on fish behavior. Using a systematic review and meta-analysis of 91 studies empirically testing effects of ocean acidification on fish behavior, we provide quantitative evidence that the research to date on this topic is characterized by a decline effect, where large effects in initial studies have all but disappeared in subsequent studies over a decade. The decline effect in this field cannot be explained by 3 likely biological explanations, including increasing proportions of studies examining (1) cold-water species; (2) nonolfactory-associated behaviors; and (3) nonlarval life stages. Furthermore, the vast majority of studies with large effect sizes in this field tend to be characterized by low sample sizes, yet are published in high-impact journals and have a disproportionate influence on the field in terms of citations. We contend that ocean acidification has a negligible direct impact on fish behavior, and we advocate for improved approaches to minimize the potential for a decline effect in future avenues of research.

Pest detection dogs for wood boring longhorn beetles

Invasive alien species are increasing due to globalization. Their spread has resulted in global economic losses. Asian [Anoplophora glabripennis (Motschulsky)] (ALB) and citrus [A. chinensis (Forster)] (CLB) longhorn beetles are two introduced wood borers which contribute to these economic losses e.g. the destruction of tree plantations. Early detection is key to reduce the ecological influence alongside the detrimental and expensive eradication. Dogs (Canis lupus familiaris) can detect these insects, potentially at an early stage. We trained two privately owned dogs to investigate their use as detection tools. We tested the dog's ability to discriminate ALB and CLB from native wood borers by carrying out double-blind and randomized experiments in three search conditions; (1) laboratory, (2) semi-field and (3) standardized field. For condition one, a mean sensitivity of 80%, specificity of 95% and accuracy of 92% were achieved. For condition two and three, a mean sensitivity of 88% and 95%, specificity of 94% and 92% and accuracy of 92% and 93% were achieved. We conclude that dogs can detect all types of traces and remains of ALB and CLB and discriminate them from native wood borers and uninfested wood, but further tests on live insects should be initiated.

Biases in ecological research: attitudes of scientists and ways of control

The properties of the human mind affect the quality of scientific knowledge through the insertion of unconscious biases during the research process. These biases frequently cause overestimation of the effects under study, thereby violating the reproducibility of the research and potentially leading to incorrect conclusions in subsequent research syntheses. We explored the level of knowledge about biases and attitudes to this problem by analysing 308 responses of ecology scientists to a specifically developed survey. We show that knowledge about biases and attitude towards biases depend on the scientist’s career stage, gender and affiliation country. Early career scientists are more concerned about biases, know more about measures to avoid biases, and twice more frequently have learned about biases from their university courses when compared with senior scientists. The respondents believe that their own studies are less prone to biases than are studies by other scientists, which hampers the control of biases in one’s own research. We conclude that education about biases is necessary, but not yet sufficient, to avoid biases because the unconscious origin of biases necessitates external intervention to combat them. Obligatory reporting of measures taken against biases in all relevant manuscripts will likely enhance the reproducibility of scientific results.

Chronic exposure to urban noise during the vocal learning period does not lead to increased song frequencies in zebra finches

Abstract

It has often been observed that birds sing at a higher pitch in cities and other areas that are polluted with intense low-frequency noise. How this pattern arises remains unclear though. One prevailing idea is that songbirds adjust song frequencies to environmental noise profiles through developmental plasticity via vocal learning. However, the conclusions of previous studies testing this hypothesis are inconsistent. Here we report the findings from two song learning experiments with zebra finches (Taenopygia guttata), in which we exposed young birds to anthropogenic noise during their sensitive vocal learning period. Unlike previous studies that addressed this issue, we did not use constant synthetic noise but natural urban noise with its typical amplitude fluctuations that was broadcast at realistic sound levels. We found that noise-exposed males in neither experiment developed higher pitched songs compared to control males. This suggests that the natural fluctuations between higher and lower noise levels in cities may allow young birds to exploit relatively quiet moments to hear their tutors and themselves, permitting them to make accurate copies of even low-frequency song elements.

Significance statement

If animals are to persist in urban habitats, they often must adjust their behavior to the altered conditions. Birds in cities are often observed to sing at a higher pitch, but we are largely ignorant of how this phenomenon arises. We investigated whether low-frequency traffic noise interferes with the song learning of birds so that they develop higher pitched songs. Accordingly, we played back natural traffic noise from urban bird habitats to young birds during their learning period and then analyzed their adult songs. We found that birds that learned their songs in noise did not sing at higher frequencies compared to control males that learned their song with no noise exposure. Our results show that typical traffic noise in cities may not be sufficient to interfere with vocal learning in a way that birds develop higher-pitched songs.

Conspecific recognition of pedal scent in domestic dogs

Carnivores rely heavily on scent to communicate with conspecifics. Scent glands located on the underside of the feet provide an especially efficient way of leaving a scent trail. Although domestic dogs (Canis familiaris) are well-known for their olfactory abilities and scent marking behaviours, their use of pedal scent for communication remains unknown. We studied the reaction of intact dogs of both sexes to male and female pedal scent as well as a control sample of scent taken from the ground, using sniffing time and nostril usage as an indicator of interest level and emotional valence. In male subjects, only the sniffing duration for other males differed from the control samples, with no clear difference detected between male and female scent. Females showed no difference in the sniffing duration for any sample type. Conversely, male nostril use did not differ between the sample types, whereas females demonstrated a right nostril bias when sniffing the scent from other females and a left nostril bias when sniffing the control. We have shown that dogs recognize scent taken from the pedal glands from other dogs, although the extent to which they use this information to determine the sex of the scent depositor remains unclear.

Canines (Canis lupus familiaris) as biodetectors for conservation work: Can they discriminate the rock ptarmigan (Lagopus muta) from the willow grouse (L. lagopus) in a yes/no task?

Alpine and arctic bird populations have shown an unmistakable decrease over the last three decades, and the need for conservation is highly necessary. We investigated the use of five privately-owned dogs (Canis lupus familiaris) as a non-invasive tool to determine the presence of rock ptarmigan (Lagopus muta), through sniffing out faecal pellets, using a yes/no training regime. We carried out 36 double-blind experimental trials per dog and hypothesised that dogs could discriminate the rock ptarmigan from similar species, such as black grouse (Tetrao tetrix), western capercaillie (T. urogallus) and willow grouse (L. lagopus). Our dogs detected differences between the avian species with an average accuracy of 65.9%, sensitivity of 66.7% and specificity of 65.3%. We showed that privately-owned dogs have the potential to be used as biodetectors for conservational work within controlled laboratory conditions for declining species, but overall, only one dog was considered proficient enough. We concluded that dogs could be used as a non-invasive tool to detect the rock ptarmigan, and with further field training and testing, operate in the field for detection surveys.