Endangered Marine Mammal Research Articles

Near-Real-Time Acoustic Monitoring of Beaked Whales and Other Cetaceans Using a Seaglider™

In most areas, estimating the presence and distribution of cryptic marine mammal species, such as beaked whales, is extremely difficult using traditional observational techniques such as ship-based visual line transect surveys. Because acoustic methods permit detection of animals underwater, at night, and in poor weather conditions, passive acoustic observation has been used increasingly often over the last decade to study marine mammal distribution, abundance, and movements, as well as for mitigation of potentially harmful anthropogenic effects. However, there is demand for new, cost-effective tools that allow scientists to monitor areas of interest autonomously with high temporal and spatial resolution in near-real time. Here we describe an autonomous underwater vehicle – a glider – equipped with an acoustic sensor and onboard data processing capabilities to passively scan an area for marine mammals in near-real time. The glider was tested extensively off the west coast of the Island of Hawai'i, USA. The instrument covered approximately 390 km during three weeks at sea and collected a total of 194 h of acoustic data. Detections of beaked whales were successfully reported to shore in near-real time. Manual analysis of the recorded data revealed a high number of vocalizations of delphinids and sperm whales. Furthermore, the glider collected vocalizations of unknown origin very similar to those made by known species of beaked whales. The instrument developed here can be used to cost-effectively screen areas of interest for marine mammals for several months at a time. The near-real-time detection and reporting capabilities of the glider can help to protect marine mammals during potentially harmful anthropogenic activities such as seismic exploration for sub-sea fossil fuels or naval sonar exercises. Furthermore, the glider is capable of under-ice operation, allowing investigation of otherwise inaccessible polar environments that are critical habitats for many endangered marine mammal species.

First evidence that marine protected areas can work for marine mammals

Summary1. Marine protected areas (MPAs) have been advocated for the protection of threatened marine mammals, but there is no empirical evidence that they are effective. In 1988, the Banks Peninsula Marine Mammal Sanctuary was established to reduce gillnet mortalities of Hector’s dolphin Cephalorhynchus hectori, an endangered dolphin species endemic to New Zealand. This study assesses the effectiveness of the MPA in improving the survival rate of Hector’s dolphin at Banks Peninsula.2. Over 21 years, we undertook photo‐identification surveys of Hector’s dolphins along standardized transects from small outboard‐powered boats. From 1986 to 2006, we photographically captured 462 reliably marked individuals. We estimated mean annual survival during the pre‐sanctuary and post‐sanctuary periods by applying a Bayesian random effects capture‐recapture model to the data. Population growth was estimated from population simulations using a stage‐structured matrix model.3. We estimate a 90% probability that survival has improved between the pre‐sanctuary and post‐sanctuary periods, with estimates of mean survival probability increasing by 5·4% (from 0·863 to 0·917). This improvement in survival corresponds to a 6% increase in mean annual population growth (from 0·939 to 0·995).4. Synthesis and applications. Our study demonstrates improvement in a demographic parameter of an endangered marine mammal species following conservation action. Our results provide evidence that area‐based protection measures can be effective for marine mammals. We note that estimating demographic parameters in marine mammals requires many years of data to achieve sufficient precision to detect biologically meaningful change. MPAs should be established with a commitment to long‐term monitoring.

Mediterranean Monk Seal (Monachus monachus): Fishery Interactions in the Archipelago of Madeira

3 MOm/Hellenic Society for the Study and Protection of the Monk Seal, Solomou Street 18, 10682, Athens, Greece Abstract Marine mammal and fishery interactions have increased concurrently with human population growth and subsequent increases in demand for fish- eries products. As a result, populations of marine mammals and the livelihood of coastal fishermen have both been adversely affected. Mediterranean monk seals (Monachus monachus) are among the most endangered marine mammals in the world that have been impacted by fisheries. The aim of this study was to understand the nature and assess the magnitude of monk seal-fisheries interactions in the Archipelago of Madeira and to propose a set of con- servation measures to mitigate them. Information on interactions was collected during questionnaire sur- veys conducted at the main fishing port of Madeira, where approximately 14% of all the fishermen and 59% of all fishing vessels in the Archipelago were interviewed. Most fishermen (91%) believed that fish stocks were declining in their region, but few (1%) considered the monk seal to be the principal reason for this negative trend. Furthermore, only 30% of the fishermen interviewed had experienced monk seal-fishing gear interactions. These interac- tions occurred mainly in summer, in the morning, at depths between 0 to 50 m and below 100 m, and affected mainly hand-lines for demersal species. At the same time, no records of entangled monk seals in fishing gear were reported. Compared to other areas in the species' range, the intensity of poten- tially negative monk seal-fisheries interactions in the Archipelago of Madeira is lower, and they do not currently constitute a threat to the survival of the species. We believe that this is due to the fact that the use of fishing nets in the region has been banned, and fishers have switched to alternative, less harmful fishing methods. Proposed conserva- tion actions should include promoting environmen- tal awareness, the production of a Good Fishing Conduct manual, and the increase in surveillance and enforcement of fishing regulations.

Identification of Ciguatoxins in Hawaiian Monk Seals Monachus schauinslandi from the Northwestern and Main Hawaiian Islands

Ciguatoxins are potent algal neurotoxins that concentrate in fish preyed upon by the critically endangered Hawaiian monk seal (Monachus schauinslandi). The only report for Hawaiian monk seal exposure to ciguatoxins occurred during a 1978 mortality event when two seal liver extracts tested positive by mouse bioassay. Ciguatoxins were thus proposed as a potential threat to the Hawaiian monk seal population. To reinvestigate monk seal exposure to ciguatoxins we utilized more selective detection methods, the Neuro-2A cytotoxicity assay, to quantify ciguatoxin activity and an analytical method LC-MS/MS to confirm the molecular structure. Tissue analysis from dead stranded animals revealed ciguatoxin activity in brain, liver, and muscle, whereas analysis of blood samples from 55 free-ranging animals revealed detectable levels of ciguatoxin activity (0.43 to 5.49 pg/mL P-CTX-1 equiv) in 19% of the animals. Bioassay-guided LC fractionation of two monk seal liver extracts identified several ciguatoxin-like peaks of activity including a peak corresponding to the P-CTX-3C which was confirmed present by LC-MS/MS. In conclusion, this work provides first confirmation that Hawaiian monk seals are exposed to significant levels of ciguatoxins and first evidence of transfer of ciguatoxin to marine mammals. This threat could pose management challenges for this endangered marine mammal species.

North Atlantic right whale seasonal presence off the coast of New Jersey: Confirmation by passive acoustic monitoring and ship survey data.

North Atlantic right whales (NARW) are one of the most critically endangered marine mammals with abundance estimates for the North Atlantic population at about 438 individuals cataloged in 2008. Data presented here were part of a larger, long-term study to assess presence of marine mammals, sea turtles, and birds along the New Jersey coast in advance of wind farm development. Seasonal presence of NARW off New Jersey was characterized using static passive acoustic monitoring (PAM) and line-transect shipboard surveys. NARW upcalls were detected on 115 days over 21 months of deployment (March 2008 to December 2009) with a significant difference in number of upcalls detected between PAM stations by month (F-ratio = 3.1292, df = 22, p = 0.000). NARW upcalls were detected from March to June and September to December 2008 and from January to March and in June 2009, with the greatest number of calls detected during spring months annually. Presence of NARW was confirmed by sighting data, with sightings all seasons except summer. Four sightings were recorded: three during November, December, and January when right whales are on calving grounds farther south or in the Gulf of Maine and the fourth sighting was a cow-calf pair in May.

Range-Wide Genetic Connectivity of the Hawaiian Monk Seal and Implications for Translocation

The Hawaiian monk seal (Monachus schauinslandi) is one of the most critically endangered marine mammals. Less than 1200 individuals remain, and the species is declining at a rate of approximately 4% per year as a result of juvenile starvation, shark predation, and entanglement in marine debris. Some of these problems may be alleviated by translocation; however, if island breeding aggregates are effectively isolated subpopulations, moving individuals may disrupt local adaptations. In these circumstances, managers must balance the pragmatic need of increasing survival with theoretical concerns about genetic viability. To assess range-wide population structure of the Hawaiian monk seal, we examined an unprecedented, near-complete genetic inventory of the species (n =1897 seals, sampled over 14 years) at 18 microsatellite loci. Genetic variation was not spatially partitioned ((w) =-0.03, p = 1.0), and a Bayesian clustering method provided evidence of one panmictic population (K =1). Pairwise F(ST) comparisons (among 7 island aggregates over 14 annual cohorts) did not reveal temporally stable, spatial reproductive isolation. Our results coupled with long-term tag-resight data confirm seal movement and gene flow throughout the Hawaiian Archipelago. Thus, human-mediated translocation of seals among locations is not likely to result in genetic incompatibilities.

Establishing general principles from little truths: lessons from marine mammal research

Much of the work that we do as zoologists and publish in Journal of Zoology relates to the search for pattern in form and function (Bennett, 2008; Boyd, 2007). This quest, in many ways, tracks the relative maturity of our various disciplines. The Journal is calling for papers that cut across boundaries that traditionally separate the field of zoology from more specialized disciplines. This call for synthesis, rather than purely descriptive studies of narrow taxonomic and geographic focus, represents an exciting development in the Journal’s history and provides a vital reminder that fundamental information about how animals function is essential to our efforts to conserve species. What is less clear, however, is how we as zoologists – and how the Journal of Zoology itself – can better anticipate and meet the needs of policy-makers and conservation practitioners. In this editorial, I will focus on this question from the perspective of marine mammal research, but the central issues are relevant to both the current state of play in zoological research and the broader application of our knowledge to the conservation of species in increasingly human-dominated environments. Ken Norris, one of the pioneers of marine mammal science, once wrote that marine mammalogists were tasked with compiling ‘little truths on which future understandings . . . may be anchored’ (Pryor & Norris, 1991). This modest set of expectations reflects the fact that marine mammals are difficult to study because of their lifestyle; our studies are often based on infrequent glimpses of animals at the surface. In 1970, Ehrenfeld outlined traits that make species inherently vulnerable to extinction, inter alia large body size, long gestation period, small litter size or lengthy maternal care, formation of large breeding aggregations, high commercial value for body parts and (or) an unregulated hunt, highly restricted distribution or distribution in international waters and trans-boundary migration. This description, in whole or in part, describes most endangered marine mammal populations. Marine mammals are particularly interesting study species for zoologists because they reach anatomical and physiological extremes, some species and populations are in dire straits, the status of many others is poorly known and our ability to conserve all of them depends on receiving the best possible advice from the zoologists who know their study animals the best. Zoologists play a vital role in efforts to understand how anthropogenic activities affect wildlife, populations and ecosystems. Interpreting what is normal or abnormal cannot be done without knowing the timing of major life-history events, energy requirements, movement or migration patterns and behaviour. In setting conservation priorities, we need to know what it is about the biology of individual species that makes some of them more vulnerable to extinction than others, and how this knowledge can and should inform recovery plans. For example, marine mammals have evolved exquisite systems for underwater hearing. As our oceans become increasingly noisy places, it is crucial to understand how these top predators will respond. Even modest disturbances in the acoustic environment can disrupt whales’ foraging activities. But why do some species appear to be more tolerant of anthropogenic noise than others, even among species thought to have nearly identical hearing? Killer whales have evolved a suite of highly derived and specialized foraging tactics in sympatric and parapatric fish-eating and mammal-eating populations. Some populations capture prey using techniques such as intentional stranding, carousel feeding and tipping ice floes. Despite similar anatomical foundations within the species, will some killer whale populations be better able to adapt than others to urbanization and habitat degradation? Marine mammal science, both past and present, abounds with these sorts of conservation questions, whose answers are found in a solid understanding of the study animal’s form and function. From bycatch in gillnet fisheries to the effects of a warming planet upon migratory habits (e.g. Williams, Noren & Glenn, 2010), cetacean researchers know that the best-laid plans for conservation and management are doomed to fail if they are not based on a good understanding of the biology of target species. Journal of Zoology

A Difficult Time with the Permit Process

In the 1970s, new forms of public scrutiny were applied to the research methods of field biologists in the United States, particularly those studying endangered species and marine mammals. This paper shows how such scrutiny affected researchers' choice of research methods through an analysis of a key moment in a decade-long controversy over the conservation of bowhead whales. In 1978, researchers at the Naval Arctic Research Laboratory received funding from the Bureau of Land Management to radio-tag bowhead whales. Although this promising but still largely untested technique might have answered one of the central scientific questions in the controversy, it ultimately went unused. Technical considerations played a role in the decision not to use the technique, but the most important factor was scientists' concerns about potential backlash from Iñupiat whalers and animal protectionists. The same forces that had made marine mammalogists more influential than ever and that had put into their hands the resources necessary to develop more effective research techniques also placed serious constraints on where, when, and how they could do their research.

First Report of Acanthocheilonema spirocauda in the Mediterranean Monk Seal (Monachus monachus)

The Mediterranean monk seal (Monachus monachus) is one of the world's most endangered marine mammals. The largest population is located mainly throughout the Aegean and Ionian islands and along the coastline of southern continental Greece. We report the findings of a necropsy and discuss their potential importance to the conservation of the species. The adult female monk seal appeared to be in a good nutritional state. The main necropsy findings were injuries consistent with a violent and sudden death, including three round wounds on the ventral surface of the body and several hematomas, as well as a decomposing male fetus in the uterus. Two nematodes were found in the right ventricle of the heart; no abnormalities were observed in the lungs, pulmonary vessels, or heart. The nematodes were identified as Acanthocheilonema spirocauda. This is the first report of infection of the Mediterranean monk seal with A. spirocauda, even though this is the most common heartworm found in most pinnipeds worldwide. This parasite should be considered in health care monitoring projects of this endangered species.

Complete mitochondrial genome of the Korean spotted seal Phoca largha (Mammalia, Pinnipedia, Phocidae): Genetic differences between P. largha and Phoca vitulina

The spotted seal Phoca largha is an endangered marine mammal whose range covers wide regions of the continental shelves of the North Pacific and Arctic Oceans (Shaughnessy and Fay 1977; Mizuno et a...

A Landmark Analysis‐Based Approach to Age and Sex Classification of the Skull of the Mediterranean Monk Seal (Monachus monachus) (Hermann, 1779)

This work aimed at applying geometric morphometric analysis techniques to the skull of the Mediterranean monk seal (Monachus monachus, Hermann, 1779). Inferential analyses were performed using a non-parameteric permutation framework based on a series of skulls of different age classes belonging to individuals of both sexes. Our goal was to establish whether a statistical approach based on osteometric measurements and surface analysis of photographs of the left lateral plane of the skull may lead to a different and scientifically sound method of age and sex classification in this critically endangered marine mammal. Our data indicate that non-parametric combination methodology enables the researcher to give local assessment using a combination with domains. Developing geometric morphometric techniques in a non-parametric permutation framework could be useful in solving high dimensional and small sample size problems as well as classification problems, including zoological classification of specimens within a specific population. The Mediterranean monk seal is believed to be the world's rarest pinniped and one of the most endangered mammals of the world, with fewer than 600 individuals currently surviving. The use of shape analysis would allow new insights into the biological characteristics of the monk seal by simply extracting potentially new information on age and size from museal specimens.

A Customization of the Arc Marine Data Model to Support Whale Tracking via Satellite Telemetry

AbstractThe Arc Marine data model is a generalized template to guide the implementation of geographic information systems (GIS) projects in the marine environment. It developed out of a collaborative process involving research and industry shareholders in coastal and marine research. This template models and attempts to standardize common ocean and coastal data types to facilitate data sharing and analytical tool development. In this study, Arc Marine is extended from its core model to fit the research goals of the whale satellite‐telemetry‐tagging program of the Oregon State University Marine Mammal Institute (MMI). The study sought the best customization of the generic Arc Marine data model to enhance the key advantages of satellite telemetry for mapping the distribution and movement of endangered marine mammal species. It was found that three new groups of object classes were needed (Animal, Telemetry, and Operations). Further customization involved the development of a comprehensive framework for animal tracking with Argos satellite telemetry data. A new multidimensional data cube model was also devised, showing how this extension of Arc Marine serves as an appropriate target schema for the application of on‐line analytical processing (OLAP) tools and spatial data mining of satellite telemetry tracking datasets.

Arsenic speciation in bodily fluids of harbor seals (Phoca vitulina) and harbor porpoises (Phocoena phocoena)

Environmental context. Marine mammals play an important role in their ecosystem. As top predators they ingest a lot of arsenic from their food. In the present study bodily fluids and tissue samples of harbor seals and porpoises were investigated for arsenic speciation in order to obtain a clearer picture on their feeding habits and consequently a better understanding of the mass mortality of the animals in the North and Baltic Sea. Abstract. The total arsenic concentrations and arsenic speciation in various tissues and bodily fluids of harbor seals (Phoca vitulina) and harbor porpoises (Phocoena phocoena) were determined to obtain information about the feeding habits of these endangered marine mammals. Lower whole blood arsenic concentrations were found for fish-fed (median: 71 μg As L–1) than for free ranging seals (median: 190 μg As L–1). In porpoise liver the arsenic concentrations were higher from carcasses found in the North Sea (median: 421 μg As kg–1 wet mass) than from those inhabiting the Baltic Sea or found in the River Elbe (median: 250 μg As kg–1). The arsenic speciation in the urine, plasma, and gastric juice of seals and the urine of porpoises, collected from animals at different areas in the North and Baltic Seas, revealed the following picture: arsenobetaine was the predominant arsenic species in all measured bodily fluids. Plasma samples of seals contained only dimethylarsinic acid as additional species. In gastric juice arsenocholine and trimethylarsine oxide were found at trace concentrations. Several arsenic compounds were identified in mammals’ urine, the major being dimethylarsinic acid and thio-dimethylarsinic acid but high variability was observed in the relative proportions of each. No correlation between degree of decay and arsenic speciation in urine could be found. This is very useful information as older carcasses can also be included in future studies. Our preliminary results are promising to obtain an insight into feeding habits of seals and porpoises by the arsenic speciation in urine.

Immunosuppression Cascade in the Florida Manatee (<I>Trichechus manatus latirostris</I>)

The Florida manatee (Trichechus manatus latirostris) is a federally endangered marine mammal that resides on both coasts of the Florida peninsula. The species faces many anthropogenic and natural threats, including boat strikes, exposure to harmful algal blooms, and cold water temperatures. We have developed a conceptual model that depicts how changes in the environment, such as reduced water temperature, can trigger an immunosuppressive cascade of interrelated diseases and pathological conditions ultimately leading to the death of the animal. Although the Florida manatee has a relatively robust immune system, rendering it resistant to several diseases, the onset of unfavorable environmental conditions has been shown to compromise the immune system, often leading to infections that make an animal more susceptible to opportunistic pathogens. In this paper, we review several common diseases of the Florida manatee and compare and contrast their symptoms. We then interrelate these diseases and generate a conceptual model of a cascade of immunosuppressive conditions originally triggered by adverse environmental conditions or one of the diseases. The end result of the cascade is the death of the animal.

Can the Vaquita Be Saved?

Scientists are embarking on a last-ditch effort to help the world9s most endangered marine mammal avoid the fate of its Chinese cousin, the baiji.

Deep genetic subdivision within a continuously distributed and highly vagile marine mammal, the Steller's sea lion (Eumetopias jubatus)

The Steller's sea lion Eumetopias jubatus is an endangered marine mammal that has experienced dramatic population declines over much of its range during the past five decades. Studies using mitochondrial DNA (mtDNA) have shown that an apparently continuous population includes a strong division, yielding two discrete stocks, western and eastern. Based on a weaker split within the western stock, a third Asian stock has also been defined. While these findings indicate strong female philopatry, a recent study using nuclear microsatellite markers found little evidence of any genetic structure, implying extensive paternal gene flow. However, this result was at odds with mark-recapture data, and both sample sizes and genetic resolution were limited. To address these concerns, we increased analytical power by genotyping over 700 individuals from across the species' range at 13 highly polymorphic microsatellite loci. We found a clear phylogenetic break between populations of the eastern stock and those of the western and Asian stocks. However, our data provide little support for the classification of a separate Asian stock. Our findings show that mtDNA structuring is not due simply to female philopatry, but instead reflects a genuine discontinuity within the range, with implications for both the phylogeography and conservation of this important marine mammal.

Gastrointestinal Helminths in the Hawaiian Monk Seal (<I>Monachus schauinslandi</I>): Associations with Body Size, Hematology, and Serum Chemistry

Gastrointestinal helminth parasites are found commonly in the Hawaiian monk seal (Monachus schauinslandi), the most endangered seal in the United States and one of the world’s most endangered pinnipeds. We studied potential associations between gastrointestinal helminth infections and body size, and hematologic and serum chemistry variables in a sample of 282 monk seals captured between 1998 and 2002 as part of a population health assessment. Based on the presence of eggs in feces, the highest prevalence of infection (78%) was for cestodes belonging to a complex of several Diphyllobothrium spp. Infections with the nematode Contracaecum turgidum were found in 29% of samples tested. Eggs of the acanthocephalan Corynosoma rauschi were found in 4% of seals examined; and the feces of four weanling seals on the French Frigate Shoals contained eggs of the recently described trematode, Heterophyopsis hawaiiensis. We used a general linear model and analysis of variance techniques with adjustment for subpopulation and age to determine whether infections with Diphyllobothrium spp. or C. turgidum were associated with changes in hematologic or serum chemistry variables and found little evidence of an effect when we compared infected with negative seals or seals in the highest quartile of egg counts with negative seals. We also conducted analyses of associations between infection and morphometric values in adjusted, age-stratified data. Infection with Diphyllobothrium spp. was associated with a decrease in axillary girth and an increase in dorsal standard length/axillary girth ratio in seals less than 2 y of age, with the effects most pronounced in seals less than 1 y of age. After adjustment for Diphyllobothrium spp., C. turgidum infection was not associated with morphometric parameters. Co-infection with Diphyllobothrium spp. and C. turgidum was not associated with differences in body size greater than those found with diphyllobothriid tapeworm infection alone. These findings suggest that intervention strategies to reduce the prevalence of tapeworm infections in immature Hawaiian monk seals should be considered as a conservation measure for this highly endangered marine mammal.

Characterization of a Novel Close-to-Root Papillomavirus from a Florida Manatee by Using Multiply Primed Rolling-Circle Amplification: Trichechus manatus latirostris Papillomavirus Type 1

By using an isothermal multiply primed rolling-circle amplification protocol, the complete genomic DNA of a novel papillomavirus was amplified from a skin lesion biopsy of a Florida manatee (Trichechus manatus latirostris), one of the most endangered marine mammals in United States coastal waters. The nucleotide sequence, genome organization, and phylogenetic position of the Trichechus manatus latirostris papillomavirus type 1 (TmPV-1) were determined. TmPV-1 is the first virus isolated from the order of Sirenia. A phylogenetic analysis shows that TmPV-1 is only distantly related to other papillomavirus sequences, and it appears in our phylogenetic tree as a novel close-to-root papillomavirus genus.

The Florida manatee and eco-tourism: toward a safe minimum standard

Development of a safe minimum standard (SMS) is proposed for the Florida manatee. Analysis was conducted to determine if preservation benefits of its recovery exceeded forgone development benefits. The manatee is a long-term endangered marine mammal that has brought millions of dollars to many coastal Florida communities. Its population has increased significantly in recent years. However, in part due to frequent motorboat collisions related injuries and deaths, the mammal continues to need protection and its long-term prospects are highly uncertain. Measurable protection benefits include local tourism revenues, as coastal Florida experiences significant manatee-related tourism, and ecological services performed by manatees through consumption of hydra in waterways, which otherwise have to be dredged. To account for the more difficult to measure preservation benefits, a contingent valuation method (CVM) survey was sent to a random sample of Citrus County, Florida residents. This county contains important winter habitat and receives significant manatee-related tourism. The CVM survey described a hypothetical market to measure household willingness to pay to protect manatees. Statistical analysis was performed on the determinants of the value of manatee preservation. Forgone net development benefits were proxied only on the cost of law enforcement of boating speed limits. The study found that the benefits of manatee protection in Citrus County greatly exceeded the development benefits foregone by approximately $8.2–$9 million, primarily related to eco-tourism. These results support an SMS policy at current population levels or higher.

Using Age Structure to Detect Impacts on Threatened Populations: a Case Study with Steller Sea Lions

Abstract: A delayed response to change is often a characteristic of long‐lived species and presents a major challenge to monitoring their status. However, rapid shifts in age structure can occur even while population size remains relatively static. We used time‐varying matrix models to study age‐structure information as a tool for improving detection of survivorship and fecundity change and status. We applied the methods to Steller sea lions ( Eumetopias jubatus), a long‐lived endangered marine mammal found throughout the North Pacific Rim. Population and newborn counts were supplemented with information on the fraction of the population that was juvenile, obtained by measuring animals in aerial photographs taken during range‐wide censuses. By fitting the model to 1976–1998 data, we obtained maximum‐likelihood estimates and 95% confidence intervals for juvenile survivorship, adult survivorship, and adult fecundity in the mid‐1980s, late 1980s, and 1990s. We used a series of nested models to test whether the data were best fit by a model with one, two, or three temporal changes in demographic rates, and we fit the models to different lengths of data to test the number of years of data needed to detect a demographic change. The declines in the early 1980s were associated with severely low juvenile survivorship, whereas declines in the 1990s were associated with disproportionately low fecundity. We repeated these analyses, fitting only to the count data without the juvenile‐fraction information, to determine whether the age‐structure information changed the conclusions and/or changed the certainty and speed with which demographic‐rate changes could be detected. The juvenile‐fraction data substantially improved the degree to which estimates from the model were consistent with field data and significantly improved the speed and certainty with which changes in demographic rates were detected.