Local assessments of marine mammals in cross-cultural environments

Biodiversity assessments by research scientists are often logistically difficult and expensive to implement in remote areas. Locally-based approaches have the potential to overcome some of these challenges by capitalising on the knowledge and capacity of local people. Many Indigenous people in northern Australia are custodians of coastal areas that support globally significant populations of tropical marine mammals, including coastal dolphins and dugongs. The objective of our study was to design and implement a locally-based approach in a cross-cultural environment to assess the distribution of marine mammals in the remote waters of the Gulf of Carpentaria, Northern Territory. The study was conducted as a partnership between Yanyuwa Aboriginal families, research scientists, government officers and the li-Anthawirriyarra Sea Rangers. We conducted a series of participatory mapping workshops to share and record local observations of dolphins and dugongs. These observations provided the longitudinal information required to inform the design of the first dedicated marine mammal vessel survey in the Gulf of Carpentaria. The vessel surveys found three species of dolphins present in the area (Australian snubfin, humpback and bottlenose dolphins), even though sightings were low; dugongs being much more common. We found that the integrative and locally-based approach built the capacity of both the li-Anthawirriyarra Sea Rangers and research scientists to assess the distribution of marine mammals. If replicated over longer time-frames and coordinated over broader spatial scales, information on distribution and abundance derived from locally-based approaches has the potential to inform the status of marine mammals.     

The whale pump: marine mammals enhance primary productivity in a coastal basin

It is well known that microbes, zooplankton, and fish are important sources of recycled nitrogen in coastal waters, yet marine mammals have largely been ignored or dismissed in this cycle. Using field measurements and population data, we find that marine mammals can enhance primary productivity in their feeding areas by concentrating nitrogen near the surface through the release of flocculent fecal plumes. Whales and seals may be responsible for replenishing 2.3×10(4) metric tons of N per year in the Gulf of Maine's euphotic zone, more than the input of all rivers combined. This upward "whale pump" played a much larger role before commercial harvest, when marine mammal recycling of nitrogen was likely more than three times atmospheric N input. Even with reduced populations, marine mammals provide an important ecosystem service by sustaining productivity in regions where they occur in high densities.     

A review of Killer Whale interactions with other marine mammals: predation to co-existence

Killer Whales are well-known as predators of other marine mammals, including the large Sperm and baleen whales. Members of all marine mammal families, except the river dolphins and manatees, have been recorded as prey of Killer Whales; attacks have been observed on 20 species of cetaceans, 14 species of pinnipeds, the Sea Otter, and the Dugong. Ecological interactions have not been systematically studied and further work may indicate that the Killer Whale is a more important predator for some populations than previously believed. Not all behavioural interactions between Killer Whales and other marine mammal species result in predation, however. Some involve 'harassment' by the Killer Whales, feeding by both species in the same area, porpoises playing around Killer Whales, both species apparently 'ignoring' each other, and even apparently unprovoked attacks on Killer Whales by sea lions. These non-predatory interactions are relatively common. We conclude that interactions between Killer Whales and marine mammals are complex, involving many different factors that we are just beginning to understand.     

Mass mortality in marine mammals: Its implications for population dynamics and genetics

The death of tens of thousands of common seals (Phoca vitulina) around the coast of Europe in 1988 provoked wide interest in the popular press, but it also raised questions about the importance of mass mortality in the dynamics of marine mammal populations. Here, we summarize published information on the occurrence of mass mortalities among marine mammals and review the mathematical models that have been developed to investigate the role of such disasters in population dynamics. We conclude that mass mortalities may play a more important role than density-dependent factors in the dynamics of some marine mammal populations. This, in combination with recent improvements in our understanding of the structure of these populations, has important implications for their genetics and evolution.     

Metallothioneins in marine mammals.

Metallothioneins (MTs) have been detected in livers and kidneys of 10 marine mammals species (Pinnipeds and Odontocetes). Characterization of renal MTs of striped dolphin has shown that the protein has two isoforms (MT-1 and MT-2) with a molecular weight estimated around 6,800. MT concentrations also vary widely in marine mammals tissues (from 58 to 1,200 microg x g(-1) ww) underlying the numerous parameters involved: physiological status, pregnancy, age, diet. The participation of this protein in metal detoxification has been investigated since high levels of cadmium (Cd) and mercury (Hg) have been measured in livers and kidneys of marine mammals. It has been suggested that those animals can mitigate at least in part, the toxic effects of Cd and Hg through binding to MTs. The percentage of the cytosolic Cd bound to MTs can reach almost 100%. On the contrary, the percentage of hepatic and renal Hg bound to MT is very low (generally less than 10%) and this metal is mainly associated with selenium (HgSe) under a detoxified form in the insoluble fraction of the tissues. MTs appear to play a minor role in the binding and detoxification of Hg by marine mammals. On the contrary, close and dynamic interactions occur between Cd and MTs. Cytosolic MTs appear as a potential short term way of detoxification of Cd accumulated from diet. Long-term detoxification would imply a sequestration of the metal under a precipitated form (e.g. in lysosomes).     

Biochemical aspects of pressure tolerance in marine mammals

Some marine mammals can dive to depths approaching 2000 m. At these hydrostatic pressures (200 atm), some fish species show alterations in enzyme structure and function that make them pressure-tolerant. Do marine mammals also possess biochemical adaptations to withstand such pressures? In theory, biochemical alterations might occur at the control of enzymatic pathways, by impacting cell membrane fluidity changes or at a higher level, such as cellular metabolism. Studies of marine mammal tissues show evidence of all of these changes, but the results are not consistent across species or diving depth. This review discusses whether the elevated body temperature of marine mammals imparts pressure tolerance at the biochemical level, whether there are cell membrane structural differences in marine mammals and whether whole, living cells from marine mammals alter their metabolism when pressure stressed. We conclude that temperature alone is probably not protective against pressure and that cell membrane composition data are not conclusive. Whole cell studies suggest that marine mammals either respond positively to pressure or are not impacted by pressure. However, the range of tissue types and enzyme systems that have been studied is extremely limited and needs to be expanded before more general conclusions about how these mammals tolerate elevated pressures on a biochemical level can be drawn.     

Assessing the trophic impacts of marine mammals: From metabolism to food web indices

Marine mammals are an important part of ecosystems, and their trophic role and potential impact have been increasingly studied. One key question is how these large animals interact with fisheries or compete for similar resources. Consequently, some models once used only for fisheries management are now including pinnipeds and cetaceans. However, fish and marine mammals do not share the same ecology and bioenergetics, and complex ecosystem models may not be the best way to assess the impact of pinnipeds or cetaceans in food webs. Indeed, simpler methods based on thermodynamics might give us reasonable answers with limited amounts of data. Here, we present an assessment of two different approaches to assess the trophic role of marine mammals in the northern Gulf of St. Lawrence (Canada): mixed trophic impacts (MTI) based on ecosystem modeling and surface index (SI) impact based on bioenergetics. Our results show that while modeling represents a good way of getting a holistic view of the role of marine mammals in ecosystems, trophic impact estimates based on fundamental thermodynamics principles can also give us answers requiring less data. The body surface area approach presented here might provide a practical tool for ecologists, who are not necessarily ecosystem modelers, to study this issue.     

Revisiting the cost of carnivory in mammals

Predator–prey relationships play a key role in the evolution and ecology of carnivores. An understanding of predator–prey relationships and how this differs across species and environments provides information on how carnivorous strategies have evolved and how they may change in response to environmental change. We aim to determine how mammals overcame the challenges of living within the marine environment; specifically, how this altered predator–prey body mass relationships relative to terrestrial mammals. Using predator and prey mass data collected from the literature, we applied phylogenetic piecewise regressions to investigate the relationship between predator and prey size across carnivorous mammals (51 terrestrial and 56 marine mammals). We demonstrate that carnivorous mammals have four broad dietary groups: small marine carnivores (< 11 000 kg) and small terrestrial carnivores (< 11 kg) feed on prey less than 5 kg and 2 kg, respectively. On average, large marine carnivores (> 11 000 kg) feed on prey equal to 0.01% of the carnivore's body size, compared to 45% or greater in large terrestrial carnivores (> 11 kg). We propose that differences in prey availability, and the relative ease of processing large prey in the terrestrial environment and small prey in marine environment, have led to the evolution of these novel foraging behaviours. Our results provide important insights into the selection pressures that may have been faced by early marine mammals and ultimately led to the evolution of a range of feeding strategies and predatory behaviours.     

Biomarkers of DNA damage in marine mammals.

Certain environmental contaminants found in marine mammals have been shown to cause DNA damage and cancer. The micronuclei (MN), sister chromatid exchange (SCE) and/or chromosome aberration (CA) assays were used to assess baseline (spontaneous) levels of DNA damage in blood lymphocytes of individuals of the relatively healthy and lightly contaminated Arctic beluga whale (Delphinapterus leucas), Sarasota Bay, FL, bottlenose dolphin (Tursiops truncatus) and Northwestern Atlantic grey (Halichoerus grypus) and harp (Phoca groenlandicus) seal populations. MN cell (MNC) frequencies ranged between 2 and 14/1000 binucleated (BN) cells and were statistically similar between species. In bottlenose dolphins, MNC frequency was correlated with age and was significantly higher in females than in males. No intraspecific variation in MNC frequency was found in beluga whales. Intraspecific variation was not tested in seals due to the small sample size. Frequencies of SCEs and total CAs, excluding gaps, ranged, respectively, between 1 and 15 SCE(s)/per cell and 4-6 CAs/100 cells in beluga whales. SCE and CA frequencies did not vary with age or sex in beluga whales. The MN, SCE and CA assays were found to be practical tools for the detection of DNA damage in marine mammals and could be used in the future to compare DNA damage between relatively lightly and highly contaminated populations.     

Review of stress in marine mammals

There has been a growing concern over the last few decades about theeffects of environmental stress, including anthropogenic impacts, onmarine mammals. This paper provides an overview of the wide range ofanthropogenic stressors that marine mammals may encounter and the levelof understanding on their potential effects. Sources of stress andphysiological responses of the animals are explored. Many of the lifehistory traits of marine mammals (i.e., long-life spans, late maturity,relatively low reproductive potential, and feeding high in the foodchain), make them susceptible to various anthropogenic stressors. Sincemarine mammals are exposed to a diverse array of multiple stressors,this paper focuses on three case studies (acute and chronic effects fromoil spills; chronic effects from environmental contaminants, andfishery-induced stress) to emphasize potential relevant hazards and toprovide a perspective on the use of marine mammals in assessingecosystem health. Additional research to enhance our understanding ofstress on marine mammals and to provide the science needed to guidemanagement decisions is recommended.     

Effects of parasites on marine mammals

This report examines the broad range of organisms which can parasitize marine mammals, and identifies those which we feel have the greatest impact on individuals and populations.Many parasites colonize and damage the integument in some way. Only the sucking lice of seals are associated with debilitating disease. In addition, at least one species, E. horridus can serve as intermediate host of the seal heartworm, D. spirocauda.Of the few protozoa, the one deserving most attention is Sarcocystis sp. Its ubiquitous distribution challenges our understanding of coccidian life cycles as currently perceived.Acanthocephalans and cestodes are rarely associated with clinically significant illness. It is intriguing that cetaceans and pinnipeds serve as mammalian intermediate hosts for larval tetraphyllidians destined to mature in elasmobranchs.Digeneans occupy the gastrointestinal tract and severely damage liver and pancreas of cetaceans. Nasitrema sp. infects cranial sinuses of small odontocetes, and enters the brain, thereby leading to stranding and death in selected populations.Nematodes represent the broadest group of parasites. Pseudaliids often infect the respiratory system, causing sufficient damage to affect survival. There is no evidence that Stenums sp., a pseudaliid inhabiting the cranial sinuses of some whales and dolphins, plays any role in mass strandings, as has been popularly suggested. Filarioids are highly pathogenic in pinnipeds and are probably responsible for significant mortality, especially in young animals. Anisakine nematodes in the stomach are of little consequence to the host. The role of marine mammals in transmitting the parasites to commercially exploited fish stocks is a public health issue. The only other parasite which represents a threat to humans is Trichinella spiralis, which is widespread in Arctic mammals.The Crassicaudinae are the largest nematodes in cetaceans. Evidence is accumulating that the damage they cause in cranial bone, mammary tissue and the urinary tract may influence productivity and survival among certain groups.Most of our understanding of the parasites of marine mammals derives from studies on specimens which come ashore. The information is fragmentary, and suffers from our inability to follow the progress of infection and the overall condition of the parasitized animal. Yet we might conclude that the parasitism we see is as advanced as can be tolerated by the host. Weak animals retreat from the protection of the herd, become vulnerable to predators, and probably cannot survive in an environment which places heavy demands on thermoregulation, respiration and mobility.     

中国濒危兽类保护遗传学研究进展与展望

我国是全球生物多样性大国,拥有包括大熊猫、金丝猴、华南虎、麋鹿、白鱀豚等特有物种和旗舰物种在内的丰富兽类资源。近几十年来,土地利用模式转变、盗猎、环境污染、气候变化等因素使许多兽类物种面临生存威胁,导致物种遗传多样性丧失。而遗传多样性是生物多样性的基本组成部分,决定了物种和种群能否长期生存。保护遗传学作为保护生物学的一大分支学科,旨在通过遗传学分析探明种群遗传变异和物种濒危的遗传学机制。近40年来,随着研究手段和技术的不断发展,我国兽类保护遗传学在遗传多样性和近交水平评估、景观遗传学、生态遗传学和圈养种群遗传管理等方面都取得了重要成果。然而,未来人类社会发展可能为濒危兽类带来的威胁依然存在,高通量测序等新技术的进一步发展则能够帮助我们更加深入地了解濒危物种和种群遗传适应与濒危机制,从而实现对濒危兽类的有效管理与保护。     

The applicability of metapopulation theory to large mammals

Metapopulation theory has become a common framework in conservation biology and it is sometimes suggested that a metapopulation approach should be used for management of large mammals. However, it has also been suggested that metapopulation theory would not be applicable to species with long generations compared to those with short ones. In this paper, we review how and on what empirical ground metapopulation terminology has been applied to insects, small mammals and large mammals. The review showed that the metapopulation term sometimes was used for population networks which only fulfilled the broadest possible definition of a metapopulation, i.e. they were subpopulations connected by migrating individuals. We argue that the metapopulation concept should be reserved for networks that also show some kind of metapopulation dynamics. Otherwise it applies to almost all populations and loses its substance. We found much empirical support for metapopulation dynamics in both insects and small mammals, but not in large mammals. A possible reason is the methods used to confirm the existence of metapopulation dynamics. For insects and small mammals, the common approach is to study population turnover through patch occupancy data. Such data is difficult to obtain for large mammals, since longer temporal scales need to be covered to record extinctions and colonizations. Still, many populations of large mammals are exposed to habitat fragmentation and the resulting subpopulations sometimes have high risks of extinction. If there is migration between the subpopulations, the metapopulation framework could provide valuable information on their population dynamics. We suggest that a metapopulation approach can be interesting for populations of large mammals, when there are discrete breeding subpopulations and when these subpopulations have different growth rates and demographic fates. Thus, a comparison of the subpopulations’ demographic fates, rather than subpopulation turnover, can be a feasible alternative for studies of metapopulation dynamics in large mammals.     

The extracellular epidermal compartment of mammals

The structure and function of the intercorneocyte cement of the corneal layer of epidermis in mammals has been reviewed on the basis of the author's and published data. Two functions of the layer have been considered: a water-tight barrier and a desquamation. Chemical structure of the barrier has been characterized. Comparison of the barrier in water and terrestrial mammals suggest that the peculiarities of the barrier correlate with different pathways of keratinization. Factors that determine the adhesion have been described. The authors show the possibility to use natural models for studying the processes of keratinization and, in particular, functioning the intercellular compartment of the corneal layer.     

Introduced mammals in Australian rangelands: Future threats and the role of monitoring programmes in management strategies

Abstract In the present paper, we have provided an initial assessment of the current and future threats to biodiversity posed by introduced mammals (predators and herbivores) inhabiting the Australian rangelands, exploring trends in populations and options for management. Notably, rabbits have declined in recent years in the wake of rabbit haemorrhagic disease, populations of feral camels have increased dramatically and foxes appear to have moved northwards, thereby threatening native fauna within an expanded range. Following on, we developed a framework for monitoring the impacts of introduced mammals in the Australian rangelands. In doing so, we considered the key issues that needed to be considered in designing a monitoring programme for this purpose and critically evaluated the role of monitoring in pest animal management. Finally we have provided a brief inventory of current best‐practice methods of estimating the abundance of introduced mammal populations in the Australian rangelands with some comments on new approaches and their potential applications.     

Monitoring exposure to avian influenza viruses in wild mammals

• 1 Avian influenza (AI) viruses primarily circulate in wild waterfowl populations and are occasionally transmitted to domestic poultry flocks. However, the possible roles of other wildlife species, such as wild mammals, in AI virus ecology have not been adequately addressed.
• 2 Due to their habitat and behaviour, many wild mammals may be capable of transmitting pathogens among wild and domestic populations. Exposure to AI viruses has been reported in an array of wild and domestic animals. The presence of wild mammals on farms has been identified as a risk factor for at least one poultry AI outbreak in North America. These reports suggest the need for seroprevalence studies examining the exposure of wild mammals to AI viruses.
• 3 Serological tests are routinely used to assess domestic poultry, domestic swine and human exposure to influenza A viruses, but these tests have not been validated for use in wild mammals. As such, some of these protocols may require adjustments or may be inappropriate for use in serology testing of wild mammals. Herein, we review these serological techniques and evaluate their potential usefulness in AI surveillance of wild mammals. We call for care to be taken when applying serological tests outside their original area of validation, and for continued assay verification for multiple species and virus strains.

     

Oxidative metabolic profiles of Brucella strains isolated from marine mammals: contribution to their species classification

Since the 1990s, Brucella strains not matching the characteristics of any of the six conventional species have been isolated worldwide from marine mammals. In this study, 31 Brucella strains isolated from various marine mammals were examined for their oxidative metabolic pattern on 12 amino-acid and carbohydrate substrates. Three main oxidative profiles different from those of the Brucella terrestrial mammal strains were identified for the marine mammal strains: one gathering strains isolated from pinnipeds and two gathering strains from cetaceans. Thus, both oxidative metabolism results and previous molecular studies are in agreement with the proposal of two new Brucella species, Brucella pinnipediae and Brucella cetaceae, to classify the Brucella strains isolated from marine mammals, and are also in accordance with a classification of species of the Brucella genus based on host preference.     

Obtaining high-quality DNA from elusive small mammals using low-tech hair snares

Noninvasive sampling approaches are becoming increasingly important for enabling genetic studies of wildlife populations. While a number of methods have been described to noninvasively sample hair from carnivores and medium-sized mammals, they have largely remained untested in elusive small mammals. Here we describe a novel and inexpensive noninvasive hair snare targeted at an elusive small mammal, the American pika (Ochotona princeps). We explore the quality of the sample by assessing PCR amplification success of mitochondrial and nuclear DNA fragments across four commercially available DNA isolation kits and two different quantities of hair in a factorial design. Additionally, we determined the sex of the individual samples using PCR–RFLP of ZFX/ZFY loci. We found that our snare is effective in obtaining hair that yield DNA of sufficient quality and quantity to successfully amplify a range of mitochondrial and nuclear fragment sizes. Specifically, we found the greatest success in amplifying mitochondrial DNA, nuclear microsatellites and ZFX/ZFY loci using at least 25 hairs as starting material and the DNA IQ™ system. The hair snares thus provide a cost-effective and minimally intrusive approach to sample elusive or rare small mammals. We anticipate that this approach will be useful to obtain samples for molecular studies of the ecology, evolution and conservation of small, elusive mammals.     

Intrinsic rate of increase,body size,and specific metabolic rate in marine mammals

Summary Hennemann (1983) provided empirical support for McNab's (1980) hypothesis that a higher specific metabolic rate (SMR) in mammals translates into a higher intrinsic rate of increase (r _m ). However, the few marine mammals in Hennemann's data base were excluded from any detailed analyses because their high rates of metabolism but only average or low values of r _m (p. 106) were thought to reflect trade-offs between maintenance and production necessary to compensate for heat loss in aquatic environments (Hennemann 1983, also see McNab 1980).To investigate further the relationships among r _m , body size, and specific metabolic rate in marine mammals (pinnepeds, sirenians, and cetaceans), r _m was estimated for 37 populations using published life-history data and Cole's (1954) equation (Hennemann 1983). Estimates of r _m in relation to body size in marine mammals were generally within the 95% confidence limits calculated for terrestrial mammals using Hennemann's data. Contrary to Hennemann's (1983) observations, eight of these populations had an r _m which was higher in relation to body size than predicted by the average terrestrial mammalian relationship. Furthermore, for marine mammal populations where suitable data were available, r _m was correlated with specific metabolic rate (r=0.85, P0.035) and all the estimates were again within the 95% confidence limits established from data for terrestrial mammals (Hennemann 1983). It is premature, therefore, to reject the hypothesis that marine mammals do not differ significantly from terrestrial mammals in their allocation of energy for maintanance and reproduction.