The effect of close approaches for tagging activities by small research vessels on the behavior of humpback whales (Megaptera novaeangliae)

Small research vessels are often used as platforms for tagging activities to collect behavioral data on cetaceans and they have the potential to disturb that group or individual. If this disturbance is ignored, results and conclusions produced by that study could be inaccurate. Here land‐based behavioral data of migrating humpback whales (Megaptera novaeangliae) (n = 29) were used to determine the effect of close approaches for tagging by research vessels on their diving, movement and surface behaviors. Groups of whales were tagged, using digital recording tags, by small research vessels, as part of a behavioral response study. In groups that were approached for tagging, temporary changes in movement behaviors during close approaches were found, with subsequent recovery to “pre‐approach” levels. In female‐calf groups more long‐term changes in travel speed were found. Results suggest that, although close approaches for tagging by small vessels may cause behavioral changes in humpback whales, this change may be small and temporary. However, in female‐calf groups, the behavioral change may be greater and longer lasting. This study shows that when using small vessels for behavioral research, disturbance, and recovery should be measured to ensure integrity of data used for other analyses.     

Evidence for the functions of surface‐active behaviors in humpback whales (Megaptera novaeangliae)

As part of their social sound repertoire, migrating humpback whales (Megaptera novaeangliae) perform a large variety of surface‐active behaviors, such as breaching and repetitive slapping of the pectoral fins and tail flukes; however, little is known about what factors influence these behaviors and what their functions might be. We investigated the potential functions of surface‐active behaviors in humpback whale groups by examining the social and environmental contexts in which they occurred. Focal observations on 94 different groups of whales were collected in conjunction with continuous acoustic monitoring, and data on the social and environmental context of each group. We propose that breaching may play a role in communication between distant groups as the probability of observing this behavior decreased significantly when the nearest whale group was within 4,000 m compared to beyond 4,000 m. Involvement in group interactions, such as the splitting of a group or a group joining with other whales, was an important factor in predicting the occurrence of pectoral, fluke, and peduncle slapping, and we suggest that they play a role in close‐range or within‐group communication. This study highlights the potentially important and diverse roles of surface‐active behaviors in the communication of migrating humpback whales.     

Diving behavior in a free‐living,semi‐aquatic herbivore,the Eurasian beaver Castor fiber

Semi‐aquatic mammals have secondarily returned to the aquatic environment, although they spend a major part of their life operating in air. Moving both on land, as well as in, and under water is challenging because such species are considered to be imperfectly adapted to both environments. We deployed accelerometers combined with a depth sensor to study the diving behavior of 12 free‐living Eurasian beavers Castor fiber in southeast Norway between 2009 and 2011 to examine the extent to which beavers conformed with mass‐dependent dive capacities, expecting them to be poorer than wholly aquatic species. Dives were generally shallow (<1 m) and of short duration (<30 s), suggesting that the majority of dives were aerobic. Dive parameters such as maximum diving depth, dive duration, and bottom phase duration were related to the effort during different dive phases and the maximum depth reached. During the descent, mean vectorial dynamic body acceleration (VeDBA—a proxy for movement power) was highest near the surface, probably due to increased upthrust linked to fur‐ and lung‐associated air. Inconsistently though, mean VeDBA underwater was highest during the ascent when this air would be expected to help drive the animals back to the surface. Higher movement costs during ascents may arise from transporting materials up, the air bubbling out of the fur, and/or the animals’ exhaling during the bottom phase of the dive. In a manner similar to other homeotherms, beavers extended both dive and bottom phase durations with diving depth. Deeper dives tended to have a longer bottom phase, although its duration was shortened with increased VeDBA during the bottom phase. Water temperature did not affect diving behavior. Overall, the beavers’ dive profile (depth, duration) was similar to other semi‐aquatic freshwater divers. However, beavers dived for only 2.8% of their active time, presumably because they do not rely on diving for food acquisition.     

Oceanic thermal structure mediates dive sequences in a foraging seabird

1. Changes in marine ecosystems are easier to detect in upper‐level predators, like seabirds, which integrate trophic interactions throughout the food web.
2. Here, we examined whether diving parameters and complexity in the temporal organization of diving behavior of little penguins (Eudyptula minor) are influenced by sea surface temperature (SST), water stratification, and wind speed—three oceanographic features influencing prey abundance and distribution in the water column.
3. Using fractal time series analysis, we found that foraging complexity, expressed as the degree of long‐range correlations or memory in the dive series, was associated with SST and water stratification throughout the breeding season, but not with wind speed. Little penguins foraging in warmer/more‐stratified waters exhibited greater determinism (memory) in foraging sequences, likely as a response to prey aggregations near the thermocline. They also showed higher foraging efficiency, performed more dives and dove to shallower depths than those foraging in colder/less‐stratified waters.
4. Reductions in the long‐term memory of dive sequences, or in other words increases in behavioral stochasticity, may suggest different strategies concerning the exploration–exploitation trade‐off under contrasting environmental conditions.

     

Using dive behavior and active acoustics to assess prey use and partitioning by fin and humpback whales near Kodiak Island,Alaska

Near the Kodiak Archipelago, fin (Balaenoptera physalus) and humpback (Megaptera novaeangliae) whales frequently overlap spatially and temporally. The Gulf Apex Predator‐prey study (GAP) investigated the prey use and potential prey partitioning between these sympatric species by combining concurrent analysis of vertical whale distribution with acoustic assessment of pelagic prey. Acoustic backscatter was classified as consistent with either fish or zooplankton. Whale dive depths were determined through suction cup tags. Tagged humpback whales (n = 10) were most often associated with distribution of fish, except when zooplankton density was very high. Associations between the dive depths of tagged fin whales (n = 4) and the vertical distribution of either prey type were less conclusive. However, prey assessment methods did not adequately describe the distribution of copepods, a potentially significant resource for fin whales. Mean dive parameters showed no significant difference between species when compared across all surveys. However, fin whales spent a greater proportion of dive time in the foraging phase than humpbacks, suggesting a possible difference in foraging efficiency between the two. These results suggest that humpback and fin whales may target different prey, with the greatest potential for diet overlap occurring when the density of zooplankton is very high.     

Delphinid whistle production and call matching during playback of simulated military sonar

In 2007 and 2008, controlled exposure experiments were performed in the Bahamas to study behavioral responses to simulated mid‐frequency active sonar (MFA) by three groups of odontocetes: false killer whales, Pseudorca crassidens; short‐finned pilot whales, Globicephala macrorhynchus; and melon‐headed whales, Peponocephala electra. An individual in each group was tagged with a Dtag to record acoustic and movement data. During exposures, some individuals produced whistles that seemed similar to the experimental MFA stimulus. Statistical tests were thus applied to investigate whistle‐MFA similarity and the relationship between whistle production rate and MFA reception time. For the false killer whale group, overall whistle rate and production rate of the most MFA‐like whistles decreased with time since last MFA reception. Despite quite low whistle rates overall by the melon‐headed whales, statistical results indicated minor transient silencing after each signal reception. There were no apparent relationships between pilot whale whistle rates and MFA sounds within the exposure period. This variability of responses suggests that changes in whistle production in response to acoustic stimuli depend not only on species and sound source, but also on the social, behavioral, or environmental contexts of exposure.     

How does social behavior differ among sperm whale clans?

When individuals primarily associate with and learn from those who behave similarly, society and culture become closely tied. Sperm whales (Physeter macrocephalus) exhibit multilevel social structure, the levels of which are differentiated in part by characteristic cultural behaviors. Sperm whales are organized into sympatric clans, with distinctive vocal repertoires that are socially learned. Other behaviors, such as movement patterns and foraging, also differ among clans. Here we ask whether the clan partition also includes divergences in social behavior. Off the Galápagos Islands, members of two clans differed consistently in diving synchrony, heterogeneity, and temporal stability of social relationships. While number of associates (indicated by social unit, group, and cluster sizes) were similar between clans, Regular clan members dived more synchronously and had more homogeneous relationships than the Plus‐One clan members. Plus‐One social units had generally longer associations than those of the Regular clan. Differences in surface‐time coordination and quality of social relationships are likely byproducts of the clan segregation, which could affect alloparental care giving, therefore scaling up to differential calf survival rates between clans. This new dimension of behavioral divergence between sperm whale clans indicates that sympatric, socio‐cultural entities of nonhumans can also display characteristic social behavior.     

Short‐finned pilot whales (Globicephala macrorhynchus) of the Mariana Archipelago: Individual affiliations,movements, and spatial use

Little is known about short‐finned pilot whales (Globicephala macrorhynchus) in the western North Pacific outside of Japanese coastal waters. To expand understanding of short‐finned pilot whale ecology in the region, we conducted small‐boat surveys in 2010?2016 within the Mariana Archipelago to investigate individual associations, movements, spatial use, and dive behavior of short‐finned pilot whales. We collected genetic, photo‐identification, and satellite‐tag data and identified 191 distinctive individuals. A preliminary social network diagram of photo‐cataloged individuals revealed a main cluster that comprised 82% of individuals, representing all five mitochondrial DNA haplotypes identified within the population. Kernel density estimates for tagged short‐finned pilot whales (n = 11) during summer were used to identify areas with the highest probability of use (10% probability density contour), core area (50%) and home range (95%). The area with highest probability of use by short‐finned pilot whales was off the northwest side of Guam. Satellite tag data also suggest that some individuals are island‐associated year‐round. Data from five location‐dive tags demonstrated that the short‐finned pilot whales dove more often to intermediate depths at twilight and night, suggesting they may target prey that forage on the deep scattering layer as it migrates to and from the surface.     

Southeastern Pacific humpback whales (Megaptera novaeangliae) and their breeding grounds: Distribution and habitat preference of singers and social groups off the coast of Ecuador

Understanding the distribution, habitat preference, and social structure of highly migratory species at important life history stages (e.g., breeding and calving) is essential for conservation efforts. We investigated the spatial distribution and habitat preference of humpback whale social groups and singers, in relation to depth categories (<20 m, 20–50 m, and >50 m) and substrate type (muddy and mixed) on a coastal southeastern Pacific breeding ground. One hundred and forty‐three acoustic stations and 304 visual sightings were made at the breeding ground off the coast of Esmeraldas, Ecuador. Spatial autocorrelation analysis suggested singers were not randomly distributed, and Neu's method and Monte Carlo simulations indicated that singers frequented depths of <20 m and mixed substrate. Singletons, and groups with a calf displayed a preference for shallower waters (0–20 m), while pairs and groups with a calf primarily inhabited mixed bottom substrates. In contrast, competitive groups showed no clear habitat preference and exhibited social segregation from other whales. Understanding the habitat preference and distribution of humpback whales on breeding and calving grounds vulnerable to anthropogenic disturbance provides important baseline information that should be incorporated into conservation efforts at a regional scale.     

Occurrence of false killer whales (Pseudorca crassidens) and their association with common bottlenose dolphins (Tursiops truncatus) off northeastern New Zealand

On a global scale, false killer whales (Pseudorca crassidens) remain one of the lesser‐known delphinids. The occurrence, site fidelity, association patterns, and presence/absence of foraging in waters off northeastern New Zealand are examined from records collected between 1995 and 2012. The species was rarely encountered; however, of the 61 distinctive, photo‐identified individuals, 88.5% were resighted, with resightings up to 7 yr after initial identification, and movements as far as 650 km documented. Group sizes ranged from 20 to ca. 150. Results indicate that all individuals are linked in a single social network. Most observations were recorded in shallow (<100 m) nearshore waters. Occurrence in these continental shelf waters is likely seasonal, coinciding with the shoreward flooding of a warm current. During 91.5% of encounters, close interspecific associations with common bottlenose dolphins (Tursiops truncatus) were observed. Photo‐identification reveals repeat inter‐ and intraspecific associations among individuals with 34.2% of common bottlenose dolphins resighted together with false killer whales over 1,832 d. While foraging was observed during 39.5% of mixed‐species encounters, results suggest that social and antipredatory factors may also play a role in the formation of these mixed‐species groups.     

Whale killers: Prevalence and ecological implications of killer whale predation on humpback whale calves off Western Australia

Reports of killer whales (Orcinus orca) preying on large whales have been relatively rare, and the ecological significance of these attacks is controversial. Here we report on numerous observations of killer whales preying on neonate humpback whales (Megaptera novaeangliae) off Western Australia (WA) based on reports we compiled and our own observations. Attacking killer whales included at least 19 individuals from three stable social groupings in a highly connected local population; 22 separate attacks with known outcomes resulted in at least 14 (64%) kills of humpback calves. We satellite‐tagged an adult female killer whale and followed her group on the water for 20.3 h over six separate days. During that time, they attacked eight humpback calves, and from the seven known outcomes, at least three calves (43%) were killed. Overall, our observations suggest that humpback calves are a predictable, plentiful, and readily taken prey source for killer whales and scavenging sharks off WA for at least 5 mo/yr. Humpback “escorts” vigorously assisted mothers in protecting their calves from attacking killer whales (and a white shark, Carcharodon carcharias). This expands the purported role of escorts in humpback whale social interactions, although it is not clear how this behavior is adaptive for the escorts.     

Biosonar,dive, and foraging activity of satellite tracked harbor porpoises (Phocoena phocoena)

This study presents bioacoustic recordings in combination with movements and diving behavior of three free‐ranging harbor porpoises (a female and two males) in Danish waters. Each porpoise was equipped with an acoustic data logger (A‐tag), a time‐depth‐recorder, a VHF radio transmitter, and a satellite transmitter. The units were programmed to release after 24 or 72 h. Possible foraging occurred mostly near the surface or at the bottom of a dive. The porpoises showed individual diversity in biosonar activity (<100 to >50,000 clicks per hour) and in dive frequency (6–179 dives per hour). We confirm that wild harbor porpoises use more intense clicks than captive animals. A positive tendency between number of dives and clicks per hour was found for a subadult male, which stayed near shore. It showed a distinct day‐night cycle with low echolocation rates during the day, but five times higher rates and higher dive activity at night. A female traveling in open waters showed no diel rhythm, but its sonar activity was three times higher compared to the males'. Considerable individual differences in dive and echolocation activity could have been influenced by biological and physical factors, but also show behavioral adaptability necessary for survival in a complex coastal environment.     

Characterization of postdive recovery using sound recordings and its relationship to dive duration,exertion, and foraging effort of southern elephant seals (Mirounga leonina)

It is notoriously difficult to measure physiological parameters in cryptic free‐ranging marine mammals. However, it is critical to understand how marine mammals manage their energy expenditure and their diving behavior in environments where the predation risks are low and where survival is mainly linked to capacities to maintain physiological homeostasis and energy budget balance. Elephant seals are top marine predators that dive deeply and continuously when at sea. Using acoustic recorders deployed on two postbreeding southern elephant seals (SES) females, we developed methods to automatically estimate breathing frequency at the surface. Using this method, we found that seals took successive identical breaths at high frequency (0.29 Hz) when recovering at the surface and that breath count was strongly related to postdive surfacing time. In addition, dive depth was the main factor explaining surfacing time through the effects of dive duration and total underwater swimming effort exerted. Finally, we found that recovery does not only occur over one dive timescale, but over a multidive time scale for one individual. The way these predators manage their recovery will determine how they respond to the change in oceanic water column structure in the future.     

The diving behavior of blue and fin whales: is dive duration shorter than expected based on oxygen stores?

Many diving seabirds and marine mammals have been found to regularly exceed their theoretical aerobic dive limit (TADL). No animals have been found to dive for durations that are consistently shorter than their TADL. We attached time-depth recorders to 7 blue whales and 15 fin whales (family Balaenopteridae). The diving behavior of both species was similar, and we distinguished between foraging and traveling dives. Foraging dives in both species were deeper, longer in duration and distinguished by a series of vertical excursions where lunge feeding presumably occurred. Foraging blue whales lunged 2.4 (+/-1.13) times per dive, with a maximum of six times and average vertical excursion of 30.2 (+/-10.04) m. Foraging fin whales lunged 1.7 (+/-0.88) times per dive, with a maximum of eight times and average vertical excursion of 21.2 (+/-4.35) m. The maximum rate of ascent of lunges was higher than the maximum rate of descent in both species, indicating that feeding lunges occurred on ascent. Foraging dives were deeper and longer than non-feeding dives in both species. On average, blue whales dived to 140.0 (+/-46.01) m and 7.8 (+/-1.89) min when foraging, and 67.6 (+/-51.46) m and 4.9 (+/-2.53) min when not foraging. Fin whales dived to 97.9 (+/-32.59) m and 6.3 (+/-1.53) min when foraging and to 59.3 (+/-29.67) m and 4.2 (+/-1.67) min when not foraging. The longest dives recorded for both species, 14.7 min for blue whales and 16.9 min for fin whales, were considerably shorter than the TADL of 31.2 and 28.6 min, respectively. An allometric comparison of seven families diving to an average depth of 80-150 m showed a significant relationship between body mass and dive duration once Balaenopteridae whales, with a mean dive duration of 6.8 min, were excluded from the analysis. Thus, the short dive durations of blue whales and fin whales cannot be explained by the shallow distribution of their prey. We propose instead that short duration diving in large whales results from either: (1) dispersal behavior of prey; or (2) a high energetic cost of foraging.     

SPERM WHALES IN THE GULF OF CALIFORNIA: RESIDENCY, MOVEMENTS, BEHAVIOR, AND THE POSSIBLE INFLUENCE OF VARIATION IN FOOD SUPPLY

Sperm whale movements, residency, population structure, and behavior were investigated in the Gulf of California in 1998 and 1999. Variations in sperm whale movement patterns and behavior were related to changes in prey abundance (jumbo squid, Dosidicus gigas ) determined by fishery statistics. Photo-identification data revealed that seven female sperm whales moved into the Gulf of California from the Galapagos Islands, traveling up to 3,803 km. These are among the longest documented movements for female sperm whales. There were significant differences in speed and distance traveled during a dive cycle between 1998 and 1999 (low and high squid abundance). In 1999 there were also significant differences in small-scale movements and behavior between the northern and the southern part of the study area (high and low prey abundance). These results suggest that when food resources are low, sperm whales travel in straighter lines, dive for longer periods, travel larger distances during dive cycles, and at higher speed. In 1999 there were significant differences in time spent socializing in areas of high prey abundance versus areas of low abundance. All of these changes in behavior were consistent with increased foraging effort when squid abundance was low. A high proportion of mature males and first-year calves were observed in the Gulf of California, suggesting that it is an important sperm whale breeding ground.     

Identification of motivational state in adult male Atlantic walruses inferred from changes in movement and diving behavior

Motivational changes in animals are likely to be detectable retrospectively through observed changes in behavior. Breeding represents one of the strongest motivational states in mammals, and its timing is often tied to a seasonally optimal suite of environmental and physical conditions. While seasonal changes in behavior may be directly observable in some species, for others that breed cryptically or in difficult to access areas, detecting behavioral changes may only be feasible using data collected remotely. Herein, we explore whether behavioral changes can be used to infer motivational state for a wild, free‐ and wide‐ranging high arctic marine mammal, adult male Atlantic walruses (Odobenus rosmarus rosmarus). Using satellite‐relayed location and dive data from 23 adult male walruses instrumented in the Svalbard Archipelago, we identify seasonal movement to discrete geographic regions deep into winter pack ice. Adult male walrus diving behavior underwent marked seasonal movements between geographical areas that coincided with changes in light regime. At offshore wintering sites adult males (n = 4) shifted from a summer pattern of deep, long benthic dives to much shallower diving. Some males performed similar shallow, winter dive behavior at coastal locations (n = 12) suggesting that breeding might also occur around the coast of Svalbard. However, interpretation of behavioral changes of these coastal individuals was challenging. The presumed breeding sites at the winter off‐shore locations were situated in areas where polynyas are known to occur, making them a predictable resource even if they are located deep inside the winter pack‐ice. We demonstrate that remotely collected behavioral data can be used to identify seasonally explicit changes in the behavior of cryptic species.     

Reindeer habitat use in relation to two small wind farms,during preconstruction,construction, and operation

Worldwide there is a rush toward wind power development and its associated infrastructure. In Fennoscandia, large‐scale wind farms comprising several hundred windmills are currently built in important grazing ranges used for Sámi reindeer husbandry. In this study, reindeer habitat use was assessed using reindeer fecal pellet group counts in relation to two relatively small wind farms, with 8 and 10 turbines, respectively. In 2009, 1,315 15‐m² plots were established and pellet groups were counted and cleaned from the plots. This was repeated once a year in May, during preconstruction, construction, and operation of the wind farms, covering 6 years (2009–2014) of reindeer habitat use in the area. We modeled the presence/absence of any pellets in a plot at both the local (wind farm site) and regional (reindeer calving to autumn range) scale with a hierarchical logistic regression, where spatial correlation was accounted for via random effects, using vegetation type, and the interaction between distance to wind turbine and time period as predictor variables. Our results revealed an absolute reduction in pellet groups by 66% and 86% around each wind farm, respectively, at local scale and by 61% at regional scale during the operation phase compared to the preconstruction phase. At the regional, scale habitat use declined close to the turbines in the same comparison. However, at the local scale, we observed increased habitat use close to the wind turbines at one of the wind farms during the operation phase. This may be explained by continued use of an important migration route close to the wind farm. The reduced use at the regional scale nevertheless suggests that there may be an overall avoidance of both wind farms during operation, but further studies of reindeer movement and behavior are needed to gain a better understanding of the mechanisms behind this suggested avoidance.     

Response of southern right whales to simulated swim‐with‐whale tourism at Península Valdés,Argentina

Guidelines for sustainable tourism involving swimming with large whales are not well‐developed compared to those focused on programs of swimming with delphinids. From September to November 2005 and August to September 2006, we collected behavioral and movement data for southern right whales (Eubalaena australis) exposed to interactions with boats and swimmers at Península Valdés, Argentina. Whales were tracked from shore using a theodolite before, during, and after a series of directed interactions with swimmers and a boat. Resting, socializing, and surface active behavior decreased, traveling increased, and whales swam faster and reoriented more often during interactions. Responses were variable by age/sex class, with mother/calf pairs showing strongest responses. Increased levels of tourism activity are a concern, as reduction in resting time and disruption of socialization among adults, juveniles, and mother/calf pairs have unknown long‐term consequences. Additional data should be collected for whale behavior in proposed tourism and nontourism areas to build a long‐term database which can be used to determine if reactions of whales change over time. Our data suggest that swimming with whales in Chubut Province should not be legalized until further investigations are completed, especially in light of the recent southern right whale die‐offs recorded in Península Valdés.     

Social Context Modulates Predator Evasion Strategy In Guppies

Social context is a powerful mediator of behavioral decisions across animal taxa, as the presence of conspecifics comes with both costs and benefits. In risky situations, the safety conferred by the presence of conspecifics can outweigh the costs of competition for resources. How the costs and benefits of grouping influence decisions among alternative antipredator behaviors remains largely unexplored. We took advantage of the Trinidadian guppy (Poecilia reticulata) to examine the influence of social context on alternative behavioral responses to threats. We compared the frequency of active (startle) versus passive (freeze) responses to sudden acoustic stimuli in the presence and absence of conspecifics. We found that fish were relatively less likely to startle and more likely to freeze when in a group than when alone, indicating that immediate social context modulates predator evasion strategy in guppies. We suggest that these social context‐dependent changes reflect trade‐offs between survival and energy expenditure. To our knowledge, an effect of immediate social environment on startle probability has not been previously demonstrated in a teleost.     

Lack of sex‐specific movement patterns in an alien species at its invasion front – consequences for invasion speed

Efficient targeting of actions to reduce the spread of invasive alien species relies on understanding the spatial, temporal, and individual variation of movement, in particular related to dispersal. Such patterns may differ between individuals at the invasion front compared to individuals in established and dense populations due to differences in environmental and ecological conditions such as abundance of conspecifics or sex‐specific dispersal affecting the encounter rate of potential mates. We assessed seasonal and diurnal variation in movement pattern (step length and turning angle) of adult male and female raccoon dog at their invasion front in northern Sweden using data from Global Positioning System (GPS)‐marked adult individuals and assessed whether male and female raccoon dog differed in their movement behavior. There were few consistent sex differences in movement. The rate of dispersal was rather similar over the months, suggesting that both male and female raccoon dog disperse during most of the year, but with higher speed during spring and summer. There were diurnal movement patterns in both sexes with more directional and faster movement during the dark hours. However, the short summer nights may limit such movement patterns, and long‐distance displacement was best explained by fine‐scale movement patterns from 18:00 to 05:00, rather than by movement patterns only from twilight and night. Simulation of dispersing raccoon dogs suggested a higher frequency of male–female encounters that were further away from the source population for the empirical data compared to a scenario with sex differences in movement pattern. The lack of sex differences in movement pattern at the invasion front results in an increased likelihood for reproductive events far from the source population. Animals outside the source population should be considered potential reproducing individuals, and a high effort to capture such individuals is needed throughout the year to prevent further spread.