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The musteloids are the most speciose of the carnivorans and have a global distribution. They display a wide diversity of morphological and physiological form and function, which have been shaped by their adaptation to a wide variety of ecological niches, ranging from the Arctic to the tropics and deserts to the seas. This chapter explores how sever...
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... Plasticity in otter activity is expected and has been reported in different species (Kruuk, 2006). Semi-aquatic otters have adaptations that are likely to facilitate nocturnal activity, including eyes with a tapetum lucidum and well-developed iris sphincter muscles (Ballard, Sivak & Howland, 1989;Kitchener, Meloro & Williams, 2017). Although previous studies speculated that nocturnal activity in neotropical otters could be in response to anthropogenic disturbances (Garrote et al., 2020;Rheingantz et al., 2016), we suggest a non-mutually exclusive alternative hypothesis. ...
Nocturnal activity of tropical otters is rarely reported. To date no studies have documented den use by sympatric giant (Pteronura brasiliensis) and neotropical otters (Lontra longicaudis). We used camera-traps to monitor den use by sympatric otters along an equatorial Amazonian river. Camera-traps provided evidence that giant otters were more nocturnal around dens than sympatric neotropical otters. Nocturnal activity was recorded in 11% of giant otter photos (n = 14 of 125 photos), but was recorded only once for neotropical otters. Den use by giant and neotropical otters overlapped spatially and temporally but not concurrently. We hypothesize that previously reported nocturnal activity in neotropical otters is facilitated by the absence or low density of giant otters. Our results also underscore the need to use complementary techniques together with den counts for monitoring otters as sympatric species can use the same dens.
... Variability in feeding habits across populations of a species can be a cause or consequence of phenotypic changes. Given the high dietary plasticity that otter species can exhibit, this is expected to be reflected in modifications of the cranial and mandibular morphology, mainly associated with the dentition and the masticatory muscle attachment area (Kitchener et al., 2017;Meloro & Tamagnini, 2022). In this sense, some intraspecific studies on otter morphology have shown that geographical variation in skull shape is related to diet, so the difference in dietary regimens may favor (Russo et al., 2022) or be favored (Campbell & Santana, 2017) by morphological divergence. ...
The marine otter, Lontra felina, is one of the top predators of the benthic communities in the southeastern Pacific coasts, from Chimbote in Peru to Cape Horn in Chile. Despite its importance in these coastal food webs, few studies exist to date on its trophic ecology and an up-to-date comprehensive understanding is needed. A systematic review was thus done on the trophic ecology of L. felina, gathering data to address diet composition, feeding patterns and the role of diet on population variability throughout its distribution. The diet of the marine otter comprises a broad spectrum of prey items, including fish, crustaceans, mollusks, birds, echinoderms, mammals, insects, tunicates and even fruits, supporting its classification as a dietary generalist and opportunist. Quantitative analyses on dietary variation across its range revealed a feeding-related biogeographical pattern, consisting of a latitudinal gradient with a higher consumption of fish to the north and crustaceans to the south. Moreover, the feeding ecomorphology of L. felina shows that this variation in diet is linked to the phenotypic characteristics of the populations. Northern marine otters, with a higher consumption of fish, exhibit a piscivory-associated morphology (narrower skulls and longer rostrums), while southern marine otters, with a higher consumption of crustaceans, present a durophagy-associated morphology (wider skulls and shorter rostrums). Considering the genetic differences between both populations and the trophic and morphological variations described, it is possible to suggest the existence of a divergence scenario between northern and southern populations of the marine otter, whose knowledge is highly relevant for its conservation given its current status as an endangered species. Despite this, the lack of information on different topics is highlighted, which traces the long road ahead in the study of the trophic ecology of L. felina.
... While all of these may contribute to the selection for larger body mass, an aquatic habitat-dependent lifestyle is likely to play a major role in shaping selective pressures on body mass in otters because otters rely on aquatic prey and thus their activity in the water is essential for survival (Estes, 1989;Kruuk, 2006). Additionally, they possess morphological and physiological features adapted for swimming and locomotion in water (Houssaye & Botton-Divet, 2018;Kitchener et al., 2017;Taylor, 1989). The most plausible factor causing selection for larger body sizes in aquatic habitats is thermoregulation in water. ...
... As with more highly aquatic mammals, thermoregulation in water is likely to exert selection pressures on body size in otters. Another plausible factor contributing to the selection for larger body mass in otters, associated with their aquatic habitat-dependent lifestyle, is the adaptation for diving (Kitchener et al., 2017). Larger body size confers an increased diving capacity (Halsey et al., 2006;Verberk et al., 2020). ...
Some taxa of mammals live in water, all of which evolved from land-dwelling ancestors. In the family Mustelidae (Mammalia: Carnivora), most species live on land, while otters, comprising the subfamily Lutrinae, inhabit aquatic environments, which include the almost exclusively aquatic sea otters (Enhydra lutris). Thus, the transition from a terrestrial to an aquatic lifestyle has occurred within this family. Despite potentially different selection pressures on body size in aquatic and terrestrial habitats, no divergence in the evolutionary pattern of body size between otters and other mustelids has previously been shown using models of trait evolution on a phylogeny. We applied models that explicitly incorporated lineage-specific directional selection to the evolution of body mass in living mustelids. Using a simulation-based likelihood and approximate Bayesian computation approach, we demonstrated lineage-specific directional selection for larger body mass in otters, which is distinct from other mustelids. There was no evidence of a difference between sea otters and other otters in the strength of directional selection for larger body mass. Additionally, our analyses supported no difference in the rate at which body mass evolves in both directions between otters and other mustelids. These findings suggest that the evolution of body mass in otters is associated with selective advantages of larger size rather than the relaxation of constraints on body size in aquatic habitats, like other aquatic mammals such as sirenians, cetaceans, and pinnipeds.
... First, both estrus and the interval between copulation and ovulation are relatively long in mustelids compared with other Carnivora, and sperm remain viable for a long time in the female reproductive tract (Amstislavsky and Ternovskaya 2000;Ferguson and Larivière 2004a). In combination with the widespread mustelid traits of superfecundation, superfetation, and delayed implantation of the blastocyst, plus multiple mating by females, sexual competition among males is increased (e.g., through sperm competition), and diverse opportunities for cryptic mate choice by females are created (Mead 1981(Mead , 1989Yamaguchi et al. 2004Yamaguchi et al. , 2006Holland and Gleeson 2005;Dugdale et al. 2007;Broekhuizen et al. 2007;Orr and Zuk 2014;Kitchener et al. 2017). In our present state of knowledge, one can only speculate on their possible relationships to bacular traits and diversity. ...
Growth, allometry, and characteristics of a sexually selected structure in wolverine (Gulo gulo (Linnaeus, 1758)), northern river otter (Lontra canadensis (Linnaeus, 1758)), and sea otter (Enhydra lutris (Linnaeus, 1758))
... Here, we quantify 3D baculum shape complexity across a closely related group of carnivoran mammals, the Musteloidea. This closely related superfamily spans a range of body sizes and possess welldeveloped, qualitatively diverse bacula (Kitchener et al., 2017;Law et al., 2017). The largest musteloid family, Mustelidae, present increased levels of SSD compared to other carnivoran groups (Law, 2019) and many engage in post-copulatory mate guarding behaviours associated with prolonged intromission duration (Dixson, 2021), making them an interesting and appropriate focus for this investigation. ...
... Indeed, all species in the family Lutrinae are grouped with low PC1 scores, commensurate with their 'simple' shape at both coarse and fine scales. This finding is expected given the rod-like morphology of the group, which has been thought to perhaps facilitate mating in water (Kitchener et al., 2017 PCAs for alpha shapes and ariaDNE show some consistency in grouping of families with similar gross morphologies. This is not surprising given the baculum is commonly used in taxonomic studies (Abramov, 2002;Van Zyll de Jong, 1972). ...
The penis bone, or baculum, is present in many orders of mammals, although its function is still relatively unknown, mainly due to the challenges with studying the baculum in vivo. Suggested functions include increasing vaginal friction, prolonging intromission, and inducing ovulation. Since it is difficult to study baculum function directly, functional morphology can give important insights. Shape complexity techniques, in particular, are likely to offer a useful metric of baculum morphology, especially since finding homologous landmarks on such a structure is challenging. This study focuses on measuring baculum shape complexity in the Musteloidea ‐ a large superfamily spanning a range of body sizes with well‐developed, qualitatively diverse bacula. We compared two shape complexity metrics – Alpha shapes and AriaDNE and conducted analyses over a range of six different coefficients, or bandwidths, in 32 species of Musteloidea. Overall, we found that shape complexity, especially at the baculum distal tip, is associated with intromission duration using both metrics. These complexities can include hooks, bifurcations and other additional projections. In addition, alpha shapes complexity was also associated with relative testes mass. These results suggest that post copulatory mechanisms of sexual selection are probably driving the evolution of more complex shaped bacula tips in Musteloidea and are likely to be especially involved in increasing intromission duration during copulation. This article is protected by copyright. All rights reserved.
... A slender skull shape in freshwater feeding otters suggests a wider gape and a faster closure of the jaws [76]. Nevertheless, a more elongated braincase allows attachment for posterior and anterior temporalis muscles, increasing the horizontal force [77]. These traits are functional to capture fast swimming and soft prey like freshwater fish, especially salmonids. ...
... The wider zygomatic arches and taller crania in marine feeders can allow an increased area for the attachment of the masseter and temporalis jaw adductor muscles [30,78]. These muscles function primarily to close the jaw [77] and the resulting larger temporalis mass in marine feeders can allow a stronger bite force [78,22]. These characteristics are often attributed to durophagous otter species like the sea otter Enhydra lutris [76]. ...
Otters are semi-aquatic mammals specialized in feeding on aquatic prey. The Eurasian otter Lutra lutra is the most widely distributed otter species. Despite a low degree of genetic variation across its European range, the population from Great Britain exhibits distinct genetic structuring. We examined 43 skulls of adult Eurasian otters belonging to 18 sampling localities and three genetic clusters (Shetlands, Wales and Scotland). For each sample location, information regarding climate was described using bioclimatic variables from WorldClim, and information on otter diet was extracted from the literature. By using photogrammetry, 3D models were obtained for each skull. To explore any evidence of adaptive divergence within these areas we used a three dimensional geometric morphometric approach to test differences in skull size and shape between areas with genetically distinct populations, as well as the influence of diet, isolation by distance and climate. Males were significantly larger in skull size than females across all the three genetic clusters. Skull shape, but not size, appeared to differ significantly among genetic clusters, with otters from Shetland exhibiting wider zygomatic arches and longer snouts compared to otters from Wales, whereas otters from Scotland displayed intermediate traits. A significant relationship could also be found between skull shape variation, diet as well as climate. Specifically, otters feeding on freshwater fish had more slender and short-snouted skulls compared to otters feeding mostly on marine fish. Individuals living along the coast are characterised by a mixed feeding regime based on marine fish and crustaceans and their skull showed an intermediate shape. Coastal and island otters also had larger orbits and eyes more oriented toward the ground, a larger nasal cavity, and a larger distance between postorbital processes and zygomatic arch. These functional traits could also represent an adaptation to favour the duration and depth of diving, while the slender skull of freshwater feeding otters could improve the hydrodynamics.
... A number of studies have found interspecific variations in craniodental and mandibular morphology which were associated with feeding ecology across force but instead permits a wider gape and a faster jaw closure (Greaves, 1983;Preuschoft & Witzel, 2005). The distance from the jaw joint to a certain point of tooth should covary with the length of snout or jaw, number of teeth and size of individual tooth, all of which show variation among carnivorans (Asahara et al., 2016;Christiansen & Adolfssen, 2005;Kitchener et al., 2010;Kitchener et al., 2017;Radinsky, 1981aRadinsky, , 1981bVan Valkenburgh, 1989). Thus, the outlever length can vary greatly among carnivoran species. ...
... masseter muscles than Atelidae and Cebidae species that feed primarily on fruits or leaves (Terhune et al., 2015). Giant and red pandas would require high bite forces to crush bamboo leaves and shoots and they have well-developed molars with broad grinding areas (Kitchener et al., 2017;Sacco & Van Valkenburgh, 2004). Our results indicated that giant and red pandas have a distinct craniodental morphology that can generate stronger bite forces by bringing the bite point closer to the jaw joint, especially when masticating with the postcarnassial molars. ...
... Small carnivorous mustelids have an elongated braincase, providing attachment for anterior and well-developed posterior temporal muscles, which can produce powerful muscle forces (Kitchener et al., 2017). Wolverines depend heavily on carrions (Hunter, 2019;Macdonald et al., 2017) and possess extremely enlarged carnassials suitable for shearing tough or frozen flesh and crushing bones (Popowics, 2003), which may keep the canines forward and away from the jaw joint. ...
Species in the mammalian order Carnivora have extremely diverse diets. The association between diet and craniodental morphology in carnivorans has been the subject of a number of studies. The distance from the jaw joint to the tooth positions may contribute to the ability to acquire and process food because it corresponds to the outlever arm when the jaw functions as a lever to generate a bite force. A shorter outlever arm relative to the inlever arm of the masticatory muscle generates a higher bite force. This study measured the distances from the jaw joint to different points of the teeth as the outlever lengths in the crania of terrestrial Carnivora species to show that outlever lengths corrected for phylogeny and a measure of the inlever length differ according to dietary habits among carnivorans. The distance from the jaw joint to the last molar was shortest in folivores, followed by aquatic prey specialists, suggesting that consumption of tough plant materials and, to some extent, aquatic prey with hard exoskeletons has favoured the evolution of a shorter outlever to allow stronger bites with enlarged molars. In contrast, among Canidae species, a shorter outlever to canines was associated with feeding on large prey, but this association was not found across carnivorans, suggesting that the correlated evolution of a shorter outlever at the canines and specialization for feeding on large prey depends on foraging and hunting behaviours. Combined, these findings provide some evidence that distances from the jaw joint to different points of the teeth are adapted to different feeding ecologies in carnivorans.
... Las nutrias (Lutrinae) constituyen un clado de mamíferos secundariamente acuáticos que se distribuyen en América, Europa, Asia y África y ocupan tanto hábitats marinocosteros como continentales (1). Junto a los pinnípedos, son los únicos carnívoros adaptados a un estilo de vida semiacuático, lo cual se refleja en sus distintivas características anatómicas (1,2). ...
... El cráneo de las nutrias se caracteriza por ser ligeramente aplanado con una caja craneana alargada, grandes canales infraorbitarios, arcos cigomáticos relativamente delgados, el inion ubicado anterior a las crestas nucales y el proceso mastoideo expandido ventralmente debajo del meato auditivo (Anexo 1) (2,3). Las mandíbulas poseen ramas cortas con una región sinfisaria procumbente que optimiza la forma hidrodinámica del cráneo (2). ...
... El cráneo de las nutrias se caracteriza por ser ligeramente aplanado con una caja craneana alargada, grandes canales infraorbitarios, arcos cigomáticos relativamente delgados, el inion ubicado anterior a las crestas nucales y el proceso mastoideo expandido ventralmente debajo del meato auditivo (Anexo 1) (2,3). Las mandíbulas poseen ramas cortas con una región sinfisaria procumbente que optimiza la forma hidrodinámica del cráneo (2). Con respecto a la dentición, la fórmula dental más común entre las nutrias es 3.1.4.1/3.1.3.2 para el número de incisivos, caninos, premolares y molares en el cráneo y la mandíbula, respectivamente (1,4). ...
La nutria marina, Lontra felina, es un carnívoro generalista con marcadas diferencias en la dieta a lo largo de su distribución en las costas del Pacífico sudeste, pues las poblaciones del norte (Perú) son principalmente piscívoras, mientras que las del sur (Chile) son predominantemente durófagas (e.g. crustáceos). Diferencias alimenticias existen entre especies vivientes de nutrias (Lutrinae) y han sido asociadas a disparidad en las proporciones del cráneo y la mandíbula. Dado que L. felina no ha sido incluida en análisis cuantitativos, se desconoce si su anatomía corresponde con alguno de los ecomorfotipos establecidos para las nutrias –piscívoro o durófago– y si éste presenta variaciones geográficas o sexuales. El objetivo de este estudio fue establecer el ecomorfotipo de alimentación de Lontra felina en un contexto filogenético e investigar su variación morfológica intraespecífica. Utilizando morfometría geométrica, se cuantificó la morfología craneal y mandibular de especímenes de Lontra felina de Perú y Chile y otras 15 especies de mustélidos. La comparación interespecífica se realizó mediante análisis de componentes principales con mapeo filogenético y las variaciones intraespecíficas se evaluaron usando análisis discriminantes y pruebas de t. Los análisis morfométricos demostraron que la nutria marina presenta un ecomorfotipo alimenticio mixto, con características tanto del piscívoro (cráneos más alargados, planos y estrechos, mandíbulas más alargadas y procesos angulares más grandes) como del durófago (cráneos más cortos, convexos y anchos, áreas molariformes más grandes y mandíbulas más cortas). Los análisis intraespecíficos indicaron la ausencia de dimorfismo sexual, pero revelaron diferencias geográficas en la forma asociadas a la variación latitudinal en la dieta entre Perú y Chile. Así, las poblaciones de Perú exhibieron cráneos más alargados y estrechos, propios del ecomorfotipo piscívoro, y, las de Chile, cráneos más cortos y anchos, típicos del ecomorfotipo durófago. Considerando las diferencias genéticas previamente reportadas, nuestros resultados apoyan la existencia de un proceso de especiación alopátrica en marcha conducido por la dieta y cuyo conocimiento es de relevancia para su conservación.
... to study hand preferences in the whole primate order. These methods might then also be applied to 372 other dexterous and ecologically variable mammalian groups, such as musteloid carnivorans 373 (Kitchener, 2017), to test hypotheses on the evolution of manual laterality across a wider 374 phylogenetic margin. Finally, we need to acknowledge the limitations of our phylogenetic modelling 375 approach. ...
The evolution of human right-handedness has been intensively debated for decades. Manual lateralization patterns in non-human primates have the potential to elucidate evolutionary determinants of human handedness. However, restricted species samples and inconsistent methodologies have so far limited comparative phylogenetic studies. By combining original data with published literature reports, we assembled data on hand preferences for standardized object manipulation in 1,786 individuals from 38 species of anthropoid primates, including monkeys, apes, and humans. Based on that, we employ quantitative phylogenetic methods to test prevalent hypotheses on the roles of ecology, brain size and tool use in primate handedness evolution. We confirm that human right-handedness represents an unparalleled extreme among anthropoids and found taxa displaying significant population-level handedness to be rare. Species-level direction of manual lateralization was largely uniform among non-human primates and did not notably correlate with any of the selected biological predictors, nor with phylogeny. In contrast, we recovered highly variable patterns of hand preference strength, which show signatures of both ecology and phylogeny. In particular, terrestrial primates tend to display weaker hand preferences than arboreal species. These results challenge popular ideas on primate handedness evolution, especially the postural origins hypothesis. Furthermore, they point to a potential adaptive benefit of disparate lateralization strength in primates, a measure of hand preference that has often been overlooked in the past. Finally, our data show that human lateralization patterns do not align with trends found among other anthropoids, suggesting that unique selective pressures gave rise to the unusual hand preferences displayed by our species.
... The 130 detected deletions (combined length of 408 kb) overlap 125 protein-coding genes associated with cell cycle, reproduction, the immune system, development, metabolism and sensory perception. Deletions were identified in two genes involved in keratinocyte differentiation, PPHLN1 (Larsen et al. 2017) and IVL, the latter of which is also associated with hair follicle development (de Viragh et al. 1994;Kitchener et al. 2018). Additionally, two short insertions were found disrupting exon 2 of NCOA4 and exon 7 of YIPF5, genes associated with mitochondrial iron homeostasis (hem synthesis) and protein transport, respectively. ...
... Despite the notable difference in hair follicle structure and fur density between palearctic and neotropic species (Kitchener et al. 2018), we did not detect any type of variation affecting genes related to these traits in wolverine. However, we observed two gene copy gains in sable, TCHHL1, involved in hair morphogenesis (Wu et al. 2011), and CDC42, required for differentiation of hair follicle progenitor cells ). ...
Species of the mustelid subfamily Guloninae inhabit diverse habitats on multiple continents, and occupy a variety of ecological niches. They differ in feeding ecologies, reproductive strategies and morphological adaptations. To identify candidate loci associated with adaptations to their respective environments, we generated a de novo assembly of the tayra (Eira barbara), the earliest diverging species in the subfamily, and compared this with the genomes available for the wolverine (Gulo gulo) and the sable (Martes zibellina). Our comparative genomic analyses included searching for signs of positive selection, examining changes in gene family sizes, as well as searching for species-specific structural variants (SVs). Among candidate loci that appear to be associated with phenotypic traits, we observed many genes related to diet, body condition and reproduction. For the tayra, which has an atypical gulonine reproductive strategy of aseasonal breeding, we observe species-specific changes in many pregnancy-related genes. For the wolverine, a circumpolar hypercarnivore that must cope with seasonal food scarcity, we observed many specific changes in genes associated with diet and body condition. Despite restricting some of our analyses to single-copy orthologs present in all three study species, we observed many candidate loci that may be linked to species traits related to environment-specific challenges in their respective habitats.
