Scent Marking Research Articles

The role of the dopamine D1 receptor in social cognition: studies using a novel genetic rat model.

ABSTRACTSocial cognition is an endophenotype that is impaired in schizophrenia and several other (comorbid) psychiatric disorders. One of the modulators of social cognition is dopamine, but its role is not clear. The effects of dopamine are mediated through dopamine receptors, including the dopamine D1 receptor (Drd1). Because current Drd1 receptor agonists are not Drd1 selective, pharmacological tools are not sufficient to delineate the role of the Drd1. Here, we describe a novel rat model with a genetic mutation in Drd1 in which we measured basic behavioural phenotypes and social cognition. The I116S mutation was predicted to render the receptor less stable. In line with this computational prediction, this Drd1 mutation led to a decreased transmembrane insertion of Drd1, whereas Drd1 expression, as measured by Drd1 mRNA levels, remained unaffected. Owing to decreased transmembrane Drd1 insertion, the mutant rats displayed normal basic motoric and neurological parameters, as well as locomotor activity and anxiety-like behaviour. However, measures of social cognition like social interaction, scent marking, pup ultrasonic vocalizations and sociability, were strongly reduced in the mutant rats. This profile of the Drd1 mutant rat offers the field of neuroscience a novel genetic rat model to study a series of psychiatric disorders including schizophrenia, autism, depression, bipolar disorder and drug addiction.

The Wild Pig (Sus scrofa) Behavior – A Retrospective Study

Wild pigs are the most prolific, very intelligent and secretive species that over the recent past has been in a lot of conflict terms with the humans. These animals are adaptive generalists and survive in wide range of habitats worldwide. The reproductive traits of wild pigs are extraordinary showing high prolificacy so it becomes impossible to control their population. These animals have adapted to become nocturnal proving it difficult to know about their behavior. However in order in spite of these challenges the main objectives of this study was to understand the behavior and ecology of this particular species to come up the control strategies. Thus basis for documenting and understanding the wild pig behavior has dramatically evolved, contributing significantly to our understanding of these animals. In general, however, the lack of intensive field studies was attributed to the fact that wild pigs were regarded everywhere as a pest. The wild pig groups usually known as sounder’s were tracked and all findings were documented. The study period was about a year and the wild pigs were tracked and observed at the adjoining regions of the Eastern Ghats (Sathyamangalam region) and the Western Ghats (Mudumalai tiger reserve, Anaimalai tiger reserve) and of Tamil Nadu state during November, 2012 to October, 2014. A variety of behaviors were documented such as social unit organization, Habitat utilization, Daily activity patterns, Movement patterns, Modes of mobility, Home range, Male-male competition, Maternal behavior, Resting/loafing beds, Mannerism and attitudes, Vigilance behavior, Vocalizations, Wallowing, Rubbing, Symbiotic grooming behavior, Scent marking, Senses. At the end of the study we were able to precisely outlay the above the entire behavior attributes of wild pigs. These findings are necessary to understand the wild pigs and their vermin nature to combat crop raiding, eventually cutting down Human-Wild pig conflict, that will a more scientific method of conservation to avoid conflicts ending in tragic outcomes.

Movement patterns of cheetahs (Acinonyx jubatus) in farmlands in Botswana.

ABSTRACTBotswana has the second highest population of cheetah (Acinonyx jubatus) with most living outside protected areas. As a result, many cheetahs are found in farming areas which occasionally results in human-wildlife conflict. This study aimed to look at movement patterns of cheetahs in farming environments to determine whether cheetahs have adapted their movements in these human-dominated landscapes. We fitted high-time resolution GPS collars to cheetahs in the Ghanzi farmlands of Botswana. GPS locations were used to calculate home range sizes as well as number and duration of visits to landscape features using a time-based local convex hull method. Cheetahs had medium-sized home ranges compared to previously studied cheetah in similar farming environments. Results showed that cheetahs actively visited scent marking trees and avoided visiting homesteads. A slight preference for visiting game farms over cattle farms was found, but there was no difference in duration of visits between farm types. We conclude that cheetahs selected for areas that are important for their dietary and social needs and prefer to avoid human-occupied areas. Improved knowledge of how cheetahs use farmlands can allow farmers to make informed decisions when developing management practices and can be an important tool for reducing human-wildlife conflict.

The time interval between sequential mating affects the response of male meadow voles to previous mates

Male meadow voles differed in their copulatory behaviour, mating and reproductive success, and odour preferences for successively encountered mates, when the interval between pairing with two females was 1 h, 1 day, 4 days, 7 days or 10 days. Male voles had shorter latencies to first ejaculation with female 2 than with female 1 when the interval was 1 h, which may be attributed to heightened sexual arousal in males for female 2. Males also had shorter copulatory bouts with female 2 than with female 1 when the intervals between pairings were 1 h and 1 day. Shorter copulation bouts may allow more mating opportunities for both sexes and encourage multiple mating. Male voles also preferred the scent marks of female 2 to those of female 1 when the interval between pairing was 7 or 10 days, suggesting that these females were treated as distinct entities.

A Novel Computational Geometry Based Node Deployment Scheme in 3-D Wireless Sensor Network

Deployment in wireless sensor network (WSN) is an important aspect and depends on the application, the WSN is designed for. In this research, a deterministic approach for sensor deployment in three-dimensional (3D) surface has been proposed, in order to maximise the coverage. For this purpose, sectoring of the terrain approach is utilised which is based on the Voronoi diagram and then the Delaunay triangulation is performed on the sectors to establish the connectivity of the deployed nodes. The basic idea is to give a deployment technique that works for the 3D terrain. The traditional Voronoi diagram algorithm is modified for sectoring the terrain and the simulated results validate the proposed algorithm. The performance of the proposed algorithm is compared with other deployment techniques like Territorial Predator Scent Marking Algorithm (TPSMA) and random deployment on the basis of coverage ratio and uniformity and comparison show the enhanced result when compared with other techniques.

Patterns in the use of rub trees by the Eurasian Brown Bear

The behaviour of marking trees by the brown bear occurs throughout the range of presence of the species. It has recently been recognised as a mean of intra-specific chemical communication, besides the likely function of ecto-parasite removal, and evidence from grizzlies showed that scent marking of trees is mainly performed by adult males during the breeding season. However, detailed studies on this behaviour in the Euroasian brown bear are lacking. We conducted a three year study on a wild bear population of 50 individuals in the Eastern Italian Alps, using camera traps. We aimed to assess the use of trees by bears’ age and sex classes, its temporal variation, and to determine key habitat and human disturbance drivers of the intensity of use of rub trees. Camera trapping yielded more than 500 videos of bears from more than 9000 camera trapping days, age and sex classes were identified in 59% of the videos. Results showed that rubbing was mainly performed by adult males, with females and sub-adults that only occasionally rubbed. Rubbing was performed more during the breeding season, confirming that the main function of this behaviour is associated to males' breeding strategy. Olfactory investigation was performed by bears of all ages and sexes, indicating the importance of scent marking at rub trees for intra-specific communication. We used the camera trapping event rate as a raw index of intensity of usage of rub trees and found it to be affected by aspect, type of roads and passage of motor vehicles at the sites, while the passage of people did not affect it. We also estimated bear occupancy and detectability and found that the latter was influenced by trail type and distance from roads and buildings. Our study provides a first contribution to the use of rub trees by brown bears in the Alps. Download the complete issue.

Preliminary Findings On Behavioral Patterns Of The Barking Deer, Muntiacusmuntjak (Zimmermann 1780) In Captivity At Dhaka Zoo In Bangladesh

This research was conducted to document behavioral patterns of the barking deer, Muntiacus muntjak (Zimmermann 1780) in captivity. All-occurrence and ad libitum sampling methods were used opportunistically to observe 15 barking deer at Dhaka Zoo in Bangladesh from April to November, 2011.A total of 54 behavioral patterns of the barking deer was recorded and described under 13 major heads. Of which, 41 behavioral patterns were similar for males and females and 13 were sex different. The highest observation was recorded for self-directed behaviors (21.55%) followed by consuming behaviors (20.84%), investigative behaviors (17.65%), scent markings and depositions (14.53%), relaxed states (13.98%), agonistic interactions (2.63%), foraging behaviors (2.31%), sexual behaviors (1.83%), submissive behaviors (1.66%), elimination (1.25%), movements (1.23%), vocalization (0.3%) and affinitive interactions (0.23%). The behavioral patterns were almost similar for male and female with several patterns showing variations. Females consumed food and took rest more frequently than males, who spent more time in foraging and movement. Males also showed higher frequency of sexual behaviors and less submissive behaviors. Environmental sniffing (n=792) was the most frequently encountered behavior and preaching (n=l) was the least. The present findings reveal that majority of the behaviors resemble that of other cervids, but nibbling and barking are unique to this species.
 Asiat. Soc. Bangladesh, Sci. 41(2): 233-243, December 2015

Interspecific interactions between wild felids vary across scales and levels of urbanization.

Ongoing global landscape change resulting from urbanization is increasingly linked to changes in species distributions and community interactions. However, relatively little is known about how urbanization influences competitive interactions among mammalian carnivores, particularly related to wild felids. We evaluated interspecific interactions between medium- and large-sized carnivores across a gradient of urbanization and multiple scales. Specifically, we investigated spatial and temporal interactions of bobcats and pumas by evaluating circadian activity patterns, broad-scale seasonal interactions, and fine-scale daily interactions in wildland-urban interface (WUI), exurban residential development, and wildland habitats. Across levels of urbanization, interspecific interactions were evaluated using two-species and single-species occupancy models with data from motion-activated cameras. As predicted, urbanization increased the opportunity for interspecific interactions between wild felids. Although pumas did not exclude bobcats from areas at broad spatial or temporal scales, bobcats responded behaviorally to the presence of pumas at finer scales, but patterns varied across levels of urbanization. In wildland habitat, bobcats avoided using areas for short temporal periods after a puma visited an area. In contrast, bobcats did not appear to avoid areas that pumas recently visited in landscapes influenced by urbanization (exurban development and WUI habitat). In addition, overlap in circadian activity patterns between bobcats and pumas increased in exurban development compared to wildland habitat. Across study areas, bobcats used sites less frequently as the number of puma photographs increased at a site. Overall, bobcats appear to shape their behavior at fine spatial and temporal scales to reduce encounters with pumas, but residential development can potentially alter these strategies and increase interaction opportunities. We explore three hypotheses to explain our results of how urbanization affected interspecific interactions that consider activity patterns, landscape configuration, and animal scent marking. Altered competitive interactions between animals in urbanized landscapes could potentially increase aggressive encounters and the frequency of disease transmission.

EU opens door for sound marks: will scent marks follow?

For national trade mark offices in the European Union (EU) and for the Office for Harmonisation in the Internal Market (OHIM), graphical representation was the insurmountable obstacle to the registration of non-traditional trade marks, such as sound, scent and taste marks, since the Sieckmann case. The removal of the graphical representation requirement for registration, as advocated by Dr Ralf Sieckmann, recommended by the Max Planck Institute and proposed for amendment of Directive 2008/95, and Council Regulation 207/2009, will open the door for the initial registration of non-traditional trade marks in the EU.Scents, with their intimate access to the amygdala, are capable of conditioning consumers to remember a certain brand and to influence their moods. In the preparatory discussions leading up to the final drafts, sound files were mentioned as proper ways to disclose sound marks to competitors. Technology has reached a threshold whereby scents can be digitally encoded, thus travel the Internet, be stored, downloaded and decoded by the emittance of scents via affordable scent printers connected to smart phones.This and other technologies will be assessed in light of the remaining Sieckmann representability requirements: ‘clear and precise, self-contained, easily accessible, intelligible, durable and objective.’ Because scent marks can, just like sound marks, be represented with technology using digital files, the Internet and a play gadget, the ‘emancipation’ of scents into the group of sensorial trade marks that are registrable in the EU seems inevitable.

Latrine behaviour as a multimodal communicatory signal station in wild lemurs: the case of Hapalemur meridionalis

Latrine behaviour is the repeated use of specific sites for defecation/urination, and is common among most mammals, including carnivores, herbivores, marsupials and rodents. While rare among primates, latrine use has been observed among some lemurs. It has been hypothesized that group-living primates may use latrines to maintain intergroup spacing (i.e. territorial defence) and for female advertisement of sexual condition. To test these, we conducted focal follows of three neighbouring southern bamboo lemur, Hapalemur meridionalis, groups in Mandena littoral forest of southeast Madagascar. From January to December 2013, we recorded all occurrences of latrine behaviour and characterized latrine sites to determine what factors influenced returning to specific latrines. Additionally, we attempted to elucidate the functional role of scent marking at latrines. We assessed the degree of home range overlap between neighbouring groups, and recorded intergroup aggression. Overall, latrines were almost exclusively visually conspicuous sites and located in the core areas of group home ranges. Best-fit models indicated that multiply visited latrines occurred more often in core areas, and were influenced by both sexes. Glandular scent marking at latrine sites was driven by males, and occurred more during the nonmating season. Males overmarked female scent-marks less often during the mating season and more often when younger males were likely to disperse. Thus, overmarking at latrine sites may function as a mate-guarding strategy to deter new males. Latrine use supports the energy frugality hypothesis, which proposes that lemur social systems, known for female social dominance and low rates of agonism, evolved as responses to the low productivity of Malagasy forests. The deposition of olfactory cues (i.e. faeces, urine, glandular secretions) at visually conspicuous sites may convey information to neighbouring conspecifics, thus reducing the need for intergroup agonism. Overall, latrine behaviour acts as a multimodal means of intergroup communication.

The Role of Scent Marking in Mate Selection by Female Pumas (Puma concolor)

Mate selection influences individual fitness, is often based on complex cues and behaviours, and can be difficult to study in solitary species including carnivores. We used motion-triggered cameras at 29 community scrapes (i.e. scent marking locations used by multiple individuals) and home range data from 39 GPS-collared pumas (Puma concolor) to assess the relevance of communication behaviours for mate selection by female pumas in California. Female pumas visited community scrapes irregularly and visitation bouts appeared to be correlated with oestrus. Female pumas on average selected from 1.7 collared males, and selection was based on multiple cues that varied among the different time periods measured (i.e. the female’s visitation bout and in 90 days previous to the consorting event). Female mate selection over the course of a visitation bout was based on frequency of the male visitation, mass, and age. In the 90 days previous to consorting, the number of scrapes a male created was the most important contributor to selection, which was likely related to his residency status. We also found that at least 14% of females mated with multiple males, thus possibly confusing paternity. Our findings provide a mechanistic understanding of how female pumas use scent and auditory communication at community scrapes to select dominant resident males to mate with.

Mate preference for dominant vs. subordinate males in young female Syrian hamsters (Mesocricetus auratus) following chemically-accelerated ovarian follicle depletion

Life history theory predicts that selectivity for mates generally declines as females age. We previously demonstrated this phenomenon in Syrian hamsters (Mesocricetus auratus), in that older females showed reduced preference for dominant over subordinate males. To test the hypothesis that decreased reproductive quality due to aging reduces mate preference, we decoupled reproductive and chronological age by treating young female hamsters with 4-vinylcyclohexene diepoxide (VCD), which destroys ovarian follicles and functionally accelerates ovarian follicle depletion without compromising the general health of rodents. In this study, VCD effectively reduced follicle numbers in young Syrian hamsters. VCD-treated and control females were allowed to choose between a dominant and a subordinate male in a Y-maze on the day of proestrus. Both VCD-treated and control females demonstrated preference for the dominant male by leaving a greater proportion of vaginal scent marks near him, which is a behavior that females display when soliciting prospective mates. However, there was no effect of treatment on the proportion of vaginal scent marks left for the dominant male. Furthermore, ovarian follicle numbers were not significantly correlated with any behaviors in either group. We conclude that accelerated ovarian follicle depletion does not reduce mate preference in young female hamsters.

Mass spectrometry for structural analysis and quantification of the Major Urinary Proteins of the house mouse

The Major Urinary Proteins (MUPs) of the house mouse, Mus musculus domesticus, are 18–19kDa beta-barrel lipocalins that are involved in chemical communication between individuals. Many of them are excreted in urine where they play multiple roles, including coding of owner identity and transport, and slow release of bound volatile pheromones. One of them, darcin, is a pheromone in its own right and induces long-term memory for the identity and location of the scent mark owner. We have shown that mass spectrometric analysis of intact proteins, and their ion mobility behaviour, is capable of dissecting subtle structural differences between the members of this class of proteins. Moreover, mass spectrometric analysis of the intact proteins can contribute towards molecular phenotyping of MUPs. However, whilst allowing relative quantification, the ionisation propensity or gas phase properties of the individual MUPs may compromise absolute quantification. To solve the challenge of absolute quantification of MUP expression, we have designed and constructed a QconCAT built from endopeptidase LysC peptides that is capable of quantifying MUPs found in laboratory animal strains and some MUPs from wild caught individuals.

Chemosensory discrimination of identity and familiarity in koalas

Despite numerous descriptive accounts of scent marking in marsupials, rigorous experimentation is rare, and relatively little evidence exists to show that conspecifics use chemical signals to distinguish between individuals or different social groups. In this study a series of olfactory discrimination tests sought to determine whether: (1) male koala sternal scent gland secretions are individually distinctive; and (2) male koalas can differentiate between the scent of familiar and unfamiliar individuals. In the first experiment a habituation–discrimination trial demonstrated that male koalas discriminate between the scent gland secretions of different unfamiliar individuals. In a second experiment male koalas spent significantly more time investigating scent from unfamiliar males than familiar males, supporting the hypothesis that they differentiate between conspecifics based on their familiarity. Taken together these results suggest that male koalas are able to discriminate the identity and familiarity of conspecifics using chemical cues, and provide a platform for further studies investigating the functional role of olfactory communication in this species.

Will Trespassers Be Prosecuted or Assessed According to Their Merits? A Consilient Interpretation of Territoriality in a Group-Living Carnivore, the European Badger (Meles meles).

Socio-spatial interactions of Carnivores have traditionally been described using the vocabulary of territoriality and aggression, with scent marks interpreted as ‘scent fences’. Here, we investigate the role of olfactory signals in assumed territorial marking of group-living solitary foragers using European badgers Meles meles as a model. We presented anal gland secretions (n = 351) from known individuals to identifiable recipients (n = 187), to assess response-variation according to familiarity (own-group, neighbours, strangers) and spatial context (in-context: at a shared border; out-of-context: at an unshared border/ the main sett). Sniffing and over-marking (with subcaudal gland secretion) responses were strongest to anal gland secretions from strangers, intermediate to neighbouring-group and weakest to own-group members. Secretions from both, strangers and neighbours, were sniffed for longer than were own-group samples, although neighbour-secretion presented out-of-context evoked no greater interest than in-context. On an individual level, responses were further moderated by the relevance of individual-specific donor information encoded in the secretion, as it related to the physiological state of the responder. There was a trend bordering on significance for males to sniff for longer than did females, but without sex-related differences in the frequency of subcaudal over-marking responses, and males over-marked oestrous female secretions more than non-oestrous females. There were no age-class related differences in sniff-duration or in over-marking. Evaluating these results in the context of the Familiarity hypothesis, the Threat-level hypothesis, and the Individual advertisement hypothesis evidences that interpretations of territorial scent-marks depicting rigid and potentially agonistic discrimination between own- and foreign-group conspecifics are overly simplistic. We use our findings to advance conceptual understanding of badger socio-spatial ecology, and the general context of territoriality and group-range dynamics.

Interpopulational Variations in Sexual Chemical Signals of Iberian Wall Lizards May Allow Maximizing Signal Efficiency under Different Climatic Conditions.

Sexual signals used in intraspecific communication are expected to evolve to maximize efficacy under a given climatic condition. Thus, chemical secretions of lizards might evolve in the evolutionary time to ensure that signals are perfectly tuned to local humidity and temperature conditions affecting their volatility and therefore their persistence and transmission through the environment. We tested experimentally whether interpopulational altitudinal differences in chemical composition of femoral gland secretions of male Iberian wall lizards (Podarcis hispanicus) have evolved to maximize efficacy of chemical signals in different environmental conditions. Chemical analyses first showed that the characteristics of chemical signals of male lizards differed between two populations inhabiting environments with different climatic conditions in spite of the fact that these two populations are closely related genetically. We also examined experimentally whether the temporal attenuation of the chemical stimuli depended on simulated climatic conditions. Thus, we used tongue-flick essays to test whether female lizards were able to detect male scent marks maintained under different conditions of temperature and humidity by chemosensory cues alone. Chemosensory tests showed that chemical signals of males had a lower efficacy (i.e. detectability and persistence) when temperature and dryness increase, but that these effects were more detrimental for signals of the highest elevation population, which occupies naturally colder and more humid environments. We suggest that the abiotic environment may cause a selective pressure on the form and expression of sexual chemical signals. Therefore, interpopulational differences in chemical profiles of femoral secretions of male P. hispanicus lizards may reflect adaptation to maximize the efficacy of the chemical signal in different climates.

An experimental study on risk effects in a dwarf antelope,Madoqua guentheri

Risk of predation shapes the physiology, behavior, and demography of prey. Among the many studies that have examined effects of risk in ungulates, most have focused on large (> 40kg) and gregarious species. Much less is known about the effect of risk on smaller or territorial ungulates, which is a diverse group of species that can have pronounced effects on plant communities in tropical ecosystems. Using GPS telemetry, we examined spatial responses of Guenther's dik-dik (Madoqua guentheri) to scent marks from a common predator (African wild dogs, Lycaon pictus) or cattle. In response to predator scent marks, dik-diks increased fidelity within territories, avoided scent marks, and decreased use of overstory cover. Similar behaviors occurred in response to cattle scent marks, with the exception that use of overstory cover relative to controls did not change. Total amount (length) of movement did not change in response to either type of scent mark. Thus, an increase in perceived risk of predation changed the...

Communication stations: cameras reveal river otter (Lontra canadensis) behavior and activity patterns at latrines

Little is known about the behaviors river otters (Lontra canadensis) commonly exhibit when visiting latrine sites. By use of video data we constructed an ethogram to describe and quantify latrine behaviors. The most common behaviors were standing (20.5 %) and sniffing (18.6 %), lending support to the hypothesis that latrines are used for olfactory communication. Surprisingly, defecation was rarely observed (1.4 %); body rubbing occurred more than defecation (10.5 %). It is possible that, in addition to feces, urine, and anal jelly, river otters use body rubbing to scent mark. To monitor site use, we determined seasonal, monthly, and daily visitation rates and calculated visit duration. River otters most frequently visited the latrine in the winter (December and January) but the longest visits occurred in the fall. Very few visits were recorded during the summer. Latrines were most often visited at night, but nocturnal and diurnal visit durations were not different. River otters were more likely to visit the latrine and engage in a specific behavior rather than travel straight through the site. Our data supported the idea that river otters are primarily solitary mammals, with most latrine visits by single otters. However, we documented groups of up to 4 individuals using the area, and group visits lasted longer than solitary visits. Therefore, whether visits are solitary or social, latrine sites are likely to act as communication stations to transmit information between individuals.

Tiger (Panthera tigris) scent DNA: a valuable conservation tool for individual identification and population monitoring

Genetic monitoring of tiger source populations is a conservation priority, yet due to low sample sizes and poor DNA quality, scat DNA has failed to produce the powerful studies needed to inform management decisions in humid, tropical landscapes. Here, we report the first successful extraction of DNA from tiger scent marks, a hitherto neglected genetic resource. We show that tiger scent DNA quality is equal or superior to scat DNA, and as scent marks are encountered 2–8 times more frequently in the wild than scats, they constitute an important genetic resource for monitoring populations and individuals.

Modeling Behavior by Coastal River Otter (Lontra Canadensis) in Response to Prey Availability in Prince William Sound, Alaska: A Spatially-Explicit Individual-Based Approach.

Effects of climate change on animal behavior and cascading ecosystem responses are rarely evaluated. In coastal Alaska, social river otters (Lontra Canadensis), largely males, cooperatively forage on schooling fish and use latrine sites to communicate group associations and dominance. Conversely, solitary otters, mainly females, feed on intertidal-demersal fish and display mutual avoidance via scent marking. This behavioral variability creates “hotspots” of nutrient deposition and affects plant productivity and diversity on the terrestrial landscape. Because the abundance of schooling pelagic fish is predicted to decline with climate change, we developed a spatially-explicit individual-based model (IBM) of otter behavior and tested six scenarios based on potential shifts to distribution patterns of schooling fish. Emergent patterns from the IBM closely mimicked observed otter behavior and landscape use in the absence of explicit rules of intraspecific attraction or repulsion. Model results were most sensitive to rules regarding spatial memory and activity state following an encounter with a fish school. With declining availability of schooling fish, the number of social groups and the time simulated otters spent in the company of conspecifics declined. Concurrently, model results suggested an elevation of defecation rate, a 25% increase in nitrogen transport to the terrestrial landscape, and significant changes to the spatial distribution of “hotspots” with declines in schooling fish availability. However, reductions in availability of schooling fish could lead to declines in otter density over time.