Calling Behavior Research Articles

Ripple effects in a communication network: anti-eavesdropper defence elicits elaborated sexual signals in rival males.

Emitting conspicuous signals into the environment to attract mates comes with the increased risk of interception by eavesdropping enemies. As a defence, a commonly described strategy is for signallers to group together in leks, diluting each individual's risk. Lekking systems are often highly social settings in which competing males dynamically alter their signalling behaviour to attract mates. Thus, signalling at the lek requires navigating fluctuations in risk, competition and reproductive opportunities. Here, we investigate how behavioural defence strategies directed at an eavesdropping enemy have cascading effects across the communication network. We investigated these behaviours in the túngara frog (Engystomops pustulosus), examining how a calling male's swatting defence directed at frog-biting midges indirectly affects the calling behaviour of his rival. We found that the rival responds to swat-induced water ripples by increasing his call rate and complexity. Then, performing phonotaxis experiments, we found that eavesdropping fringe-lipped bats (Trachops cirrhosus) do not exhibit a preference for a swatting male compared to his rival, but females strongly prefer the rival male. Defences to minimize attacks from eavesdroppers thus shift the mate competition landscape in favour of rival males. By modulating the attractiveness of signalling prey to female receivers, we posit that eavesdropping micropredators likely have an unappreciated impact on the ecology and evolution of sexual communication systems.

Laboratory evaluation of interspecific mating between Zeugodacus fruit flies and Bactrocera dorsalis

AbstractThe increasing number of tephritid pest invasions worldwide highlights the importance of interspecific interactions among tephritid pests. The melon fly [Zeugodacus cucurbitae (Coquillett)], the pumpkin fruit fly [Zeugodacus tau (Walker)], and the oriental fruit fly [Bactrocera dorsalis (Hendel)] (all Diptera: Tephritidae) are neotropical fruit flies with overlapping distributions. Their interactions during mating hours have rarely been observed in nature due to their nocturnal behavior. Here, laboratory studies were conducted under no‐choice and choice conditions to quantify interspecific mating. The interactions during mating hours resulted in interspecific mating, which reduced conspecific mating success and interrupted mating activity patterns. Successful interspecific mating pairs of Z. cucurbitae and Z. tau were recorded in no‐choice and choice tests. Interspecific mating between male Z. cucurbitae and female Z. tau significantly reduced conspecific mating in Z. tau. Observations of the diel mating activity patterns showed that male Z. cucurbitae initiated calling behaviors earlier than Z. tau males, giving Z. cucurbitae more chances to court Z. tau. Though males of neither Zeugodacus species formed mating pairs with B. dorsalis, Zeugodacus males reduced conspecific mating in B. dorsalis in the choice trials. Thus, interspecific interactions among Z. cucurbitae, Z. tau, and B. dorsalis affected conspecific mating; interrupted conspecific mating activity patterns were recorded in all three species. This information could be used to improve management practices.

Gymnandrosoma aurantianum (Lepidoptera: Tortricidae): Calling Rhythm and Effect of Age on Female Sex Pheromone Titer and Male Antennal Responses.

The macadamia nut borer, Gymnandrosoma aurantianum Lima (Lepidoptera: Tortricidae), is the main pest of Macadamia integrifolia Maiden & Betche (Proteales: Proteaceae) in Central America. Despite its importance, there is little information on its reproductive behavior. We studied the calling behavior and effect of age on female sex pheromone production and male antennal response to the pheromone. Calling behavior of G. aurantianum females occurred at the onset of scotophase, between 17:00 and 20:00h. The mean time spent calling was 64min. It was observed that 30% of the 50 females exhibited a calling posture characterized by extrusion of the pheromone gland from the tip of the abdomen and they spread their wings slightly. Female age had no influence on the sex pheromone production, while male antennal response increased with age and pheromone dosage. The information obtained in this work contributes to understanding the sexual behavior of G. aurantianum and thus to the creation of strategies to control this important pest in macadamia.

A dataset for benchmarking Neotropical anuran calls identification in passive acoustic monitoring

Global change is predicted to induce shifts in anuran acoustic behavior, which can be studied through passive acoustic monitoring (PAM). Understanding changes in calling behavior requires automatic identification of anuran species, which is challenging due to the particular characteristics of neotropical soundscapes. In this paper, we introduce a large-scale multi-species dataset of anuran amphibians calls recorded by PAM, that comprises 27 hours of expert annotations for 42 different species from two Brazilian biomes. We provide open access to the dataset, including the raw recordings, experimental setup code, and a benchmark with a baseline model of the fine-grained categorization problem. Additionally, we highlight the challenges of the dataset to encourage machine learning researchers to solve the problem of anuran call identification towards conservation policy. All our experiments and resources have been made available at https://soundclim.github.io/anuraweb/.

Beyond the individual: An improved telecom fraud detection approach based on latent synergy graph learning

The development of telecom technology not only facilitates social interactions but also inevitably provides the breeding ground for telecom fraud crimes. However, telecom fraud detection is a challenging task as fraudsters tend to commit co-fraud and disguise themselves within the mass of benign ones. Previous approaches work by unearthing differences in calling sequential patterns between independent fraudsters, but they may ignore synergic fraud patterns and oversimplify fraudulent behaviors. Fortunately, graph-like data formed by traceable telecom interaction provides opportunities for graph neural network (GNN)-based telecom fraud detection methods. Therefore, we develop a latent synergy graph (LSG) learning-based telecom fraud detector, named LSG-FD, to model both sequential and interactive fraudulent behaviors. Specifically, LSG-FD introduces (1) a multi-view LSG extractor to reconstruct synergy relationship-oriented graphs from the meta-interaction graph based on second-order proximity assumption; (2) an LSTM-based calling behavior encoder to capture the sequential patterns from the perspective of local individuals; (3) a dual-channel based graph learning module to alleviate the disassortativity issue (caused by the camouflages of fraudsters) by incorporating the dual-channel frequency filters and the learnable controller to adaptively aggregate high- and low-frequency information from their neighbors; (4) an imbalance-resistant model trainer to remedy the graph imbalance issue by developing a label-aware sampler. Experiment results on the telecom fraud dataset and another two widely used fraud datasets have verified the effectiveness of our model.

Studying Customer Behavior in the Libyan Telecoms Market using Data Visualization

In general, the main benefit of data visualization is that it provides a better understanding of complex data and enables faster decision-making.This study on call detail records (CDRs) and SMS activity data visualization was conducted to fully understand the customer behavior patterns and culture in the Libyan telecom market.A big telecom data (261 GB) was collected for CDRs between 28 March and 22 April 2020. This includes 19 working days, three Fridays and four Saturdays. The data visualization results show that the weekend SMS and call activity pattern shows a completely different behavior compared to other days of the week. Call behavior between 12:00 and 7:00 is generally almost the same. The peak times for calls on weekdays are between 11:30 and 13:00 and for SMS between 19:30 and 22:00. Furthermore, the analysis of SMS activities does not reflect customer behavior, but much of the SMS activity is the result of electronic payment services during shopping. However, Libyan culture is more about making phone calls than sending SMS messages. since the number of calls at dawn is minimal, the number of SMS increased slightly at this time. In order to retain customers, decision makers should consider these results and develop appropriate plans and strategies. However, in order to reduce call congestion and increase efficiency, decision makers should set appropriate pricing during peak or pre-peak and post-peak hours to convert many customers before or after peak hours.Also, they should somehow encourage customers to use SMS instead of calls.

대학생 진로결정수준과 진로준비행동의 관계에서 진로소명의 매개효과

Objectives The purpose of this study was to explore the relationship among career decision level, career calling, and career preparation behavior. The present study thus examined the impact of career calling on the relationship between career decision level and career preparation behavior of Korean college students.
 Methods For this aim, 283 Korean college students participated in this study and their career decision levels, career calling, and career preparation behavior were measured. Uni-variate, bivariate, and hierarchical multivariate analysis were conducted. Baron and Kenny(1986)’s mediation test procedure and Sobel test were used to analyze the data.
 Results As results, there was a significant and positive relationship between career decision level, career calling and career preparation behavior. This means higher career decision level would be able to lead higher levels of career preparation behavior and career calling. In addition, when demographic variables, age, gender, grade, major field were controlled, we found the mediational effect of career calling on the relationship between career decision level and career preparation behavior.
 Conclusions We offered implications that to lead the higher levels of career preparation behavior of college students, it would be important to focus on increasing their levels of career calling.

Social regulation of androgenic hormones and gestural display behavior in a tropical frog

Many animals use forms of gesture and dance to communicate with conspecifics in the breeding season, though the mechanisms of this behavior are rarely studied. Here, we investigate the hormone basis of such visual signal behavior in Bornean rocks frogs (Staurois parvus). Our results show that males aggregating at breeding waterfalls have higher testosterone (T) levels, and we speculate that this hormone increase is caused by social cues associated with sexual competition. To this end, we find that T levels in frogs at the waterfall positively predict the number waving gestures—or “foot flags”—that males perform while competing with rivals. By contrast, T does not predict differences in male calling behavior. In these frogs, vocal displays are used largely as an alert signal to direct a rival's attention to the foot flag; thus, our results are consistent with the view that factors related to reproductive context drive up T levels to mediate displays most closely linked to male-male combat, which in this case is the frog's elaborate gestural routine.

Effect of Environmental Variables on African Penguin Vocal Activity: Implications for Acoustic Censusing.

Global biodiversity is in rapid decline, and many seabird species have disproportionally poorer conservation statuses than terrestrial birds. A good understanding of population dynamics is necessary for successful conservation efforts, making noninvasive, cost-effective monitoring tools essential. Here, we set out to investigate whether passive acoustic monitoring (PAM) could be used to estimate the number of animals within a set area of an African penguin (Spheniscus demersus) colony in South Africa. We were able to automate the detection of ecstatic display songs (EDSs) in our recordings, thus facilitating the handling of large datasets. This allowed us to show that calling rate increased with wind speed and humidity but decreased with temperature, and to highlight apparent abundance variations between nesting habitat types. We then showed that the number of EDSs in our recordings positively correlated with the number of callers counted during visual observations, indicating that the density could be estimated based on calling rate. Our observations suggest that increasing temperatures may adversely impact penguin calling behaviour, with potential negative consequences for population dynamics, suggesting the importance of effective conservation measures. Crucially, this study shows that PAM could be successfully used to monitor this endangered species' populations with minimal disturbance.

Interspecific differences in the effects of masking and distraction on anti-predator behavior in suburban anthropogenic noise.

Predation is a common threat to animal survival. The detection of predators or anti-predator communication signals can be disrupted by anthropogenic noise; however, the mechanism by which responses are affected is unclear. Masking and distraction are the two hypotheses that have emerged as likely explanations for changes in behavior in noise. Masking occurs when the signal and noise fall within the same sensory domain; noise overlapping the energy in the signal reduces signal detection. Distraction can occur when noise in any sensory domain contributes to a greater cognitive load, thereby reducing signal detection. Here, we used a repeated measures field experiment to determine the relative contributions of masking and distraction in mediating reduced anti-predator responses in noise. We recorded the approaches and vocalizations of black-capped chickadees (Poecile atricapillus), tufted titmice (Baeolophus bicolor), and white-breasted nuthatches (Sitta carolinensis) to both visual and acoustic cues of predator presence, either with or without simultaneous exposure to anthropogenic noise. Titmice increased their calling to both visual and acoustic cues of predator presence. However, there was no significant effect of noise on the calling responses of titmice regardless of stimulus modality. Noise appeared to produce a distraction effect in chickadees; however, this effect was small, suggesting that chickadees may be relatively unaffected by low levels of anthropogenic noise in suburban environments. White-breasted nuthatch calling behavior was affected by the interaction of the modality of the predator stimulus and the noise condition. Nuthatches had a delayed response to the predator presentations, with a greater calling rate following the presentation of the acoustic stimulus in quiet compared to the presentation of the acoustic stimulus in noise. However, there was no difference in calling rate between the quiet and noise conditions for the visual stimulus. Together this suggests that even moderate levels of noise have some masking effect for white-breasted nuthatches. We suggest that the mechanisms through which noise influences anti-predator behavior may depend on the social roles, foraging ecology and auditory capabilities of each species.

Seasonal and diel variations in the acoustic communication of tree hyraxes in Taita Hills, Kenya

Tree hyraxes (Dendrohyrax spp.) are highly vocal, elusive nocturnal mammals that live in forests across much of Sub-Saharan Africa. Here, we studied how tree hyrax acoustic communication activity varies during the year in a moist montane forest in Taita Hills, Kenya. Our study increases the knowledge about the seasonal and diel variation in tree hyrax calling activity and on the impact of exogenous factors on the calling behavior of the species. A group of tree hyraxes called 700–2000 times during the night, and calling rate was highest during dry season months. Calling activity was bimodal, with peaks between 19.00 and 20.00 h in the evening and between 04.00 and 05.00 h in the morning; however, counter-calling bouts occurred throughout the night. Singing peaked in May, possibly coinciding with the species’ mating season. Calling activity decreased during full moon phases, probably because the animals felt vulnerable to predation. Tree hyrax calling was suppressed by rain, as rainfall is a powerful acoustic competitor. Annual changes in night temperature, the background chorus of vocalizing orthopterans, or the competing calls of nocturnal primates did not reduce tree hyrax calling rates. The latter suggests that sympatric nocturnal mammals have adapted to each other’s calls as an intrinsic feature of the soundscape of their forest habitat.

Receptivity and Remating Propensity in Female Spodoptera litura (Fabricius) after Mating with an Irradiated Male or Its F1 Male Progeny.

The 'Inherited or F1 sterility technique' (IS), using sub-sterilized male moths, is a widely proposed pest management tool for Lepidoptera pests in general, and the tobacco cutworm Spodoptera litura (Fabr.) in particular. However, the multiple mating tendency of female moths and the ejaculate quality of male moths might influence the efficiency of this technique. Reduced ejaculate quality was observed in irradiated males, as evidenced by radiation's impact on certain bio-parameters, such as the weight of the spermatophores and their protein content, sperm count, the molecular expression of the sex peptide receptor (SPR) and egg fertility, with a greater impact in F1 male progeny. During the remating of females with untreated males, irrespective of the irradiation status of the first male, there was an increase in calling behavior, remating propensity and fertility in females, with a larger time gap between consecutive matings. The ability of F1 male progeny to check remating propensity in females 24 h after the initial mating was lower than that of unirradiated males. Partially sterile (130 Gy) males were as successful as unirradiated males in inducing the level of mating refractoriness in females. Decreased ejaculate quality in F1 male progeny could be associated with increased female receptivity during remating. Understanding the influence of male moth irradiation, insemination quality and post (initial)-mating intervals on the remating behavior of normal female moths and induced sterility might help in simulation modeling and optimizing IS insect programs.

Acoustic behavior of gray whales tagged with biologging devices on foraging grounds

Understanding the function of baleen whale acoustic signals requires the investigation of calling behaviors relative to location, timing, and behavioral state. Previous studies of gray whale (Eschrichtius robustus) vocal behavior have principally used passive recorders and been conducted primarily on breeding grounds and along migratory routes, and not areas associated with foraging. We conducted an analysis of accelerometer and acoustic data collected during 12 deployments of animal-borne tags in 2016, 2019, and 2021 on gray whales that return annually to northern Puget Sound, Washington. We identified 141 calls from gray whales in approximately 128 hours of accelerometer and/or acoustic data collected from tag deployments. The most prominent were pulsive ‘rumble-like’ calls, upsweeping tones, and moans. Using the tag’s accelerometer to identify calls produced by tagged animals enabled us to explore the behavioral context behind call production, revealing that vocalizations were made primarily at slow speeds (mean 1.03 ± 0.26 m/s-1), shallow depths (mean 7.63 ± 4.99 m), and temporally proximate to surface behavior (mean 43.3 ± 39.66 sec) most similar to non-foraging associated depth (mean 5.78 ± 1.46 m and speed (mean 1.46 ± 1.11 m/s-1) profiles. Vocalizations originating from the tagged animal occurred closer to the conclusion of a foraging event (mean 87.7 ± 119.32 min) than the beginning, with only 7% of all calls occurring during periods of feeding. This study demonstrates that gray whales remain vocal on foraging grounds and that call-associated accelerometry signals can be a valuable tool in identifying individual callers in animal-borne acoustic data.

Hybridization in heliothine moths: impacts on reproduction, pheromone communication, and pest management

Heliothine moths (Family Noctuidae : Subfamily Heliothinae) are ubiquitous crop pests with three documented species combinations known to hybridize: Helicoverpa zea x Helicoverpa armigera, H. armigera x Helicoverpa assulta, and Heliothis virescens x Heliothis subflexa. Hybrids can have advantageous traits, such as increased host range, resistance to insecticides, and increased mating success, posing serious threats to agriculture. However, deleterious traits of hybrids, such as developmental abnormalities or sterility, can be exploited for pest management. In this review, the characteristics of F1 hybrids and backcrosses are examined through a historical lens. Topics reviewed include developmental characteristics, sex pheromone synthesis and perception, mating and calling behavior, sperm morphology, gene expression, electrophysiological responses, structures of the central and peripheral nervous systems, hybrid sterility, and applications in pest control. Recommendations for future studies based on existing gaps of knowledge are given, as are proposed pest management strategies.

Animal Calling Behaviours and What This Can Tell Us about the Effects of Changing Soundscapes

The behavioural, physiological, and energetic repercussions for wildlife that result from changes in their soundscapes are increasingly being realized. To understand the effects of changing acoustic landscapes, we first must establish the importance of the acoustic sense for species to transfer information between the environment, con- and heterospecifics, and a receiver, and the functional role of calling in behaviours such as foraging, navigation, mate attraction, and weaning. This review begins with a discussion of the use of calling and the acquisition of the vocal repertoire, before providing examples from multiple taxa on the functional applications of signals and communication. The acoustic sensory mode adds to, if not being inherent in, many critical life history stages over a range of species. The potential effects on an animal resulting from a change in its perceived soundscape and disturbance on its acoustics use is outlined. This can then be used to consider the implications of an altered acoustic niche or active space in the success and survival of an individual or species. Furthermore, we discuss briefly metrics that could be used to understand the implications of these changes, or could be used to guide mitigation action to lessen the impact.

Bioacoustic Analysis for Help Identify Andestimate Distribution of Anura Due to the Effects of Ecotourism in the CA-TWA Region of Telaga Warna

Indonesia is a country with very high biodiversity and is known as Mega Biodiversity. In Indonesia found about 450 species of Anura representing about 11% of all species in the world, and 28 species ofwhich 28 live in West Java. Anura animals have a pattern of calling behavior that is essential for mating: males produce call-up behavior that attracts females and, in some species, represents the extent of their territory. Research on frogs and toads is considered necessary considering the absence of more detailed data on the bioacoustics of these frogs, especially in the West Java area, so that variations and patterns of anura sounds are known in the Telaga Warna Nature Reserve and Nature Park (CA-TWA) area and can make scientific contributions in information on variations and sound patterns owned by anura animals in terms of anura conservation in Indonesia. This research was conducted from month March-December 2018, located in Telaga Warna Nature Reserve and Nature Park, Bogor, West Java. Call the recording every 6:00 p.m. to 11:00 p.m. each night during the sampling period. The number of anura species in the villa and swamp areas is more abundant than the lake area, and the presence of Pearl maroon frogs (nyctixalus margaritifer) found in the villa and lake areas, while the Bufo melanotictus type that likes to live in the lake area. It can be seen that the villa and swamp areas are still maintained vegetation by looking at the medium density of the canopy. Steeper slope conditions help the flow of nutrients from the soil due to the erosion process and settle in flat to gentle areas. The density of the canopy in the area helps maintain the surface temperature of the land with a stable land surface temperature ranging from 15 – 21 0C.

Habitat suitability mapping using logistic regression analysis of long-term bioacoustic bat survey dataset in the Cassadaga Creek watershed (USA)

Bat species show global ecological importance, yet their numbers are declining worldwide. Understanding bat-habitat interactions is crucial in terms of developing effective conservation plans. In an effort to model bat habitat suitability in the Cassadaga Creek watershed, long-term bioacoustic bat data (spanning 2009–2020) was compiled, georeferenced and statistically analyzed using logistic regression techniques. In total, 1600 bat occurrence records from five species of bat (559 Eptesicus fuscus, 560 Lasionycteris noctivagans, 143 Lasiurus borealis, 260 Lasiurus cinereus, and 78 Myotis lucifugus) were paired with pseudo-absence points to study the relationship between bat calling behavior and land cover. All bats but Myotis lucifugus had a statistically significant relationship with forested land cover, and all bats had negative interactions with agricultural habitats. Geospatial data was coupled with the statistical output to create maps of habitat suitability and echolocation calling density. This work provides a model that can be employed worldwide to evaluate bat habitat needs or patterns in echolocation behavior. Future research will incorporate a more recently collected dataset that is of greater geographic diversity with a larger number of environmental variables in the species distribution model.

RNAi-mediated silencing of SlitPer disrupts sex pheromone communication behavior in Spodoptera litura.

The 24-hour circadian rhythm is considered crucial for insect sexual communication. However, its molecular mechanisms and signalling pathways, especially the roles of the clock gene period (Per), remain largely unclear. The sex pheromone communication behavior of Spodoptera litura displays typical circadian rhythm characteristics. Thus, it represents an excellent model for functional analyses of the clock gene Per. In this study, we investigated the potential roles of SlitPer in regulating sex pheromone communication in S. litura using RNAi, qRT-PCR, GC, and behavioral assays. The qRT-PCR results showed that the expression levels of SlitPer and two desaturase genes (SlitDes5 and SlitDes11) in the siPer group significantly differed in most time points from those in the siNC group. The dynamic variation in the three major sex pheromone titers and calling behavior of S. litura females in the siPer group were disordered. In addition, the mating rates of siPer S. litura females significantly decreased by 33.33%. The oviposition of mated siPer females was substantially reduced by 84.84%. These findings provide a fundamental basis for elucidating the molecular mechanism by which Per regulates sex pheromone communication behavior in lepidopteran species. This article is protected by copyright. All rights reserved.

Anthropogenic noise decreases activity and calling behavior in wild mice

Background Animals rely on sound to mediate a myriad of daily activities, and anthropogenic noise is a pollutant that alters the natural soundscape within which they are active. As human infrastructure expands, broadband anthropogenic noise increases, which can affect behaviors of free-living nocturnal animals. Mice are nocturnal animals that produce ultrasonic calls as part of their behavioral repertoire. Methods We assessed effects of anthropogenic and natural noise on the behaviors of wild deer mice (Peromyscus maniculatus) and woodland jumping mice (Napaeozapus insignis), two species of mice that produce ultrasonic calls. We measured activity, foraging behavior at a foraging tray, and calling behavior to broadcasts of natural and anthropogenic noise, compared to a baseline with no broadcasting, at 25 focal areas in the Southern Appalachian Mountain Range of North Carolina, USA. Results Deer mice exposed to anthropogenic noise spent less time in focal areas with broadcasted anthropogenic noise. Mice took longer to begin foraging in the presence of anthropogenic noise, they spent less time at the foraging tray, and left fewer husks but consumed the same number of seeds as mice exposed to natural noise. Deer mice were less likely than woodland jumping mice to be the first to enter the focal area and approach food when in the presence of anthropogenic noise. Both species produced few ultrasonic calls in the presence of broadcasted natural and anthropogenic noise compared to their baseline level of calling. We present the first calls recorded from woodland jumping mice. Conclusion Anthropogenic noise affects activity, foraging behavior, and calling behavior of nocturnal mice. Natural noise also affects the calling behavior of mice. Mouse species respond differently to anthropogenic noise, with deer mice appearing more sensitive to anthropogenic noise than woodland jumping mice. Responses to noise could have important effects on the ecology of mice and these two species respond differently. Species differences should be considered when mitigating the effects of noise in conservation ecology.

Potential impact of offshore human activities on gray whales (Eschrichtius robustus)

Gray whale (Eschrichtius robustus) reactions to offshore human activities have been relatively well studied compared to those of other mysticetes. Studies of short-term behavioural responses to underwater noise associated with aircraft, ships and seismic explorations indicate a 0.5 probability that whales will respond to continuous broadband noise when sound levels exceed ca 120dB2 and to intermittent noise when levels exceed ca 170dB, usually by changing their swimming course to avoid the source. Gray whales were ‘startled’ at the sudden onset of noise during playback studies, but demonstrated a flexibility in swimming and calling behaviour that may allow them to circumvent increased noise levels. Whales may be ‘harassed’ by noise from large commercial vessels, especially in shipping lanes or near busy ports. Gray whales sometimes change course and alter their swimming speed and respiratory patterns when followed by whalewatching boats. Conversely, some whales swim toward small skiffs deployed from whalewatching boats in breeding lagoons, seemingly attracted by the noise of idling outboard engines. Reported gray whale reactions to aircraft are varied and seem related to ongoing whale behaviour and aircraft altitude. Whale response to research involving tagging and biopsy sampling appears to be short term. Gray whales were seen swimming through surface oil from the Exxon Valdez oil spill along the Alaskan coast and showed only partial avoidance to natural oil seeps off the California coast. Laboratory tests suggest that gray whale baleen, and possibly skin, may be resistant to damage by oil, but spilled oil or oil dispersant in a primary feeding area could negatively affect gray whales by contaminating benthic prey. Gray whales are sometimes injured or killed in collisions with vessels or entanglement in fishing gear. Concern about the cumulative long-term impact of offshore human activities is particularly acute in the Southern California Bight, where many activities are often concurrent.