Endangered species / 1 . Mammals

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Advice on the frog is due in March next year, while advice on the remaining nine species is due in September this year. Topics Endangered species. Animals Conservation Wildlife news. Reuse this content. Most popular. The otters play an important role in controlling sea urchin populations, which would otherwise damage the kelp forest ecosystem. They were thought to be extinct from the California coast, until 50 otters were found near Big Sur.

The Florida panther is the most endangered cat in North America. With only — cats in the wild, the panther most likely would not exist without the Endangered Species Act. The only known breeding population of panthers is in south Florida, although its historic range covered the entire southeastern United States. The Florida panther is a subspecies of puma which goes by many names; mountain lion, cougar, painter, American lion. Wolves are highly social animals that live in family groups called packs.


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At the top of the food chain, they have a very important role in the ecosystem. In the years since they were reintroduced to Yellowstone National Park and central Idaho, wolves have helped reduce an overpopulation of elk in the Park, and have kept elk from lingering undisturbed in Aspen groves and along streams. Most marine mammal populations that significantly increased after ESA listing had substantial population growth Figs 2 and 3 ; Table 3.

For example, all four DPSs of humpback whales analyzed in our study showed substantial population increases Fig 2 ; Table 3. In fact, the Hawaiian DPS of humpback whale reached over 10, individuals in from only individuals estimated in Fig 2 ; Table 3. While most large whale populations trended toward recovery, the critically endangered population of the North Atlantic right whale Eubalaena glacialis increased at 4.

Grey dots are estimated number of individuals. Panels are organized by decreasing length of time listed and then in alphabetical order based on species names. Dashed vertical red lines indicate the year of ESA listing.

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For population selection criteria see methods ; for protection status see Table 1 ; and for results of fitting models see S2 Table. Panels are organized by decreasing length of time listed. North Western; and S. W: Southwest. Population Pop. First and last population abundance estimates for the time period are shown for reference. Populations of non-cetacean marine mammal species also significantly increased in abundance at relatively high growth rates since ESA protection.

The California population of the Southern sea otter Enhydra lutris nereis approximately doubled in numbers and it is likely to reach the demographic recovery criteria in the coming years Fig 3 ; Table 3. Representative populations of five marine mammal species analyzed in our study did not increase in abundance.

In contrast, two marine mammal populations significantly declined after ESA listing: the critically endangered Southern Resident killer whale Orcinus orca and the Hawaiian monk seal Neomonachus schauinslandi. Southern Resident killer whales declined at— 0. This population suffered major declines after a record high of 98 individuals in , and the last population survey estimated 76 individuals as of December , a year low Fig 2 ; Table 3. However, the population had increased to seals by Table 3.

Six of the eight populations of the five sea turtle species analyzed in our study significantly increased after ESA listing Fig 4 ; Table 3 and S2 Table. Notably, the Atlantic leatherback nesting populations within U.

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Grey dots are estimated number of nests, except number of nesting females green turtle, Hawaii population , and number of individuals green turtle, Guam population. For population selection criteria see methods ; for protection status see Table 1 ; for results of fitting models see S2 Table ; and for DPS of each population Pop. The best models for the number of nests of loggerhead turtles across index beaches of the Florida peninsula described a non-linear relationship where the number of nests substantially fluctuated since , with a record high of 65, in Fig 4.

Most representative populations of marine mammal and sea turtle species protected under the ESA that met our selection criteria significantly increased after listing, indicating population recoveries. Significant population increases for most marine mammal and sea turtle species after ESA protection demonstrate the capacity of these taxa to rebound from drastic population declines after decades of exploitation, habitat degradation, and other threats, once effective conservation measures are in place.

Our analyses confirm the hypothesis that populations of ESA-listed marine mammal and sea turtle species are more likely to be recovering the longer they stay protected under the law, regardless of whether they are listed as threatened or endangered. Previous studies support these findings for a variety of terrestrial taxa, marine birds, and anadromous fishes [ 16 , 19 , 23 , 25 , 39 , 63 ]. Thus, our results provide critical information on the recovery time for depleted marine mammal and sea turtle populations that can inform planning for effective management and ground expectations for recovery success.

Our results also support previous studies that highlight the capacity of marine mammals and sea turtles to rebound from decades of exploitation after coordinated national and international conservation efforts [ 40 , 41 , 50 , 64 , 65 ]. Population recovery of sea turtles have been linked to effective protection of nesting females and eggs, as well as bycatch reduction [ 41 , 42 ].

Here we discuss how the protections of the ESA and complementary conservation measures have been important for the recovery of ESA-listed marine mammal and sea turtle populations occurring in U. Marine mammal and sea turtle populations have greatly benefited from a major change from resource exploitation e.

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For the large whales, ESA protections facilitated the recovery of populations that were severely depleted by commercial whaling by reducing key threats such as ship strikes, entanglement in fishing gear, and pollution [ 44 , 66 , 73 — 76 ]. For example, ESA protection led to the establishment of vessel speed limits and restrictions on approaching whales too closely to lower the likelihood of death and injury from vessel strikes [ 77 — 79 ]. By triggering a depleted designation under the U.

Marine Mammal Protection Act MMPA , ESA marine mammal listings have prompted the implementation of take reduction plans to reduce injury and death from fisheries entanglement that require gear modifications, time and area closures, and vessel observers [ 40 , 80 ]. ESA regulations have also helped to limit acoustic harms to whales and other marine mammals by restricting U.

However, entanglement in fishing gear and collisions with vessels continue to be major threats to vulnerable large whale species [ 82 ]. For example, the North Atlantic right whale population has suffered a significant decline in the last decade due to entanglement in fishing gear and vessel collisions, threats that are compromising the recovery of this critically endangered population [ 82 — 84 ]. For sea turtles within U. ESA listing prompted regulations that have reduced sea turtle bycatch mortality in commercial fisheries by requiring gear modifications e.

ESA-prompted reductions in off-road-vehicle use and night lighting on nesting beaches have promoted nesting activity [ 89 , 90 ], as has protection of important turtle nesting beaches such as National Wildlife Refuges NWR on the Atlantic coast e. Caribbean e. Virgin Islands [ 42 , 43 , 91 ].

Among the sea turtle species with remarkable recovery success are the nesting populations of leatherbacks, green turtles and loggerhead turtles, especially across Florida [ 42 , 43 , 92 ]. In addition, ESA protections have facilitated federal and state agencies e. Importantly, the successful conservation of sea turtles has also relied on international cooperation, multinational agreements, and in-country efforts to effectively protect these highly migratory species [ 41 , 42 ].

Several international conservation efforts such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora CITES which listed sea turtles in , the Inter-American Convention IAC for the protection and conservation of sea turtles, and the Convention for Migratory Species CMS which listed sea turtles in , among others, have also been important in the reduction of threats, especially trade of sea turtle products, harvest, and incidental bycatch [ 42 , 43 , 94 , 95 ]. Regional and national legislation, harvesting bans, and local conservation efforts by non-governmental groups have given protection to sea turtle species in neighboring countries that may have contributed to recovery of U.

Conservation measures for these two species were developed relatively recently and ongoing threats have not been mitigated [ 96 , 97 ]. It is likely that these populations will require more time under ESA protection as well as the adoption of robust conservation measures. In contrast, populations of one marine mammal and two sea turtle species listed for several decades showed non-significant change.

The lack of significant population changes in the Western North Atlantic stock of fin whale and the Central West Pacific DPS of green turtle may be related to lack of statistical power to detect a trend in abundance as confidence intervals of population estimates were relatively large Figs 2 and 4 ; S1 Table [ 42 , 98 ]. Alternatively, the populations of these species may be stable, but further population estimates are needed to determine stability [ 42 , 98 ]. Finally, fluctuations in the number of nests of the nesting population of loggerhead turtle across Florida beaches have been strongly correlated with ocean conditions associated with long term climate forcing such as the Atlantic Multidecadal Oscillation [ 99 ].

Endangered marine mammal species with relatively low population abundance that significantly declined after listing e. NMFS already recognizes these species among those most at-risk of extinction in the immediate future and they are considered recovery priorities because of rapid population declines [ ]. These species face several similar regional anthropogenic threats including prey reduction due to fishing, habitat degradation, toxic pollutants, disturbance from boat traffic and marine noise, fishery interactions, as well as global threats associated with climate change and ocean regime shifts that affect food availability [ — ].

Numerous conservation measures addressing anthropogenic stressors have been developed for these species and are delineated in recovery plans [ 97 , , ]. For example, NMFS established regulations to protect killer whales in Washington waters from vessel impacts in [ ]. For Hawaiian monk seals, entanglements in fishing gear, fishery interactions, and other human-caused mortalities e. In fact, after more than 50 years of continued decline, the range-wide population seems to have steadily increased in numbers since , reaching approximately 1, seals in [ ].

Recently, stronger conservation measures have been developed in high-priority action plans that focus efforts and resources to reduce threats and stabilize population declines [ ]. The outcomes of these conservation efforts will require time to be realized, although the compounding effects of climate change stressors may compromise the ability of these endangered species to rebound. Whales in this population use the waters surrounding the main Hawaiian Islands for mating and calving and migrate to feeding in areas off Southeast Alaska and northern British Columbia.

ESA listing in prompted conservation measures in Hawaii and Alaska to reduce key threats to recovery. ESA regulations restricted vessels in Hawaiian and Alaskan waters from approaching whales within yards, prohibited disrupting normal behaviors, and required slower vessel speeds to reduce the likelihood of ship strikes and minimize human disturbance [ , ]. ESA listing also prompted coordinated federal and state efforts to reduce whale entanglements in fishing gear through the Hawaiian Islands Disentanglement Network and Alaska Response Network.

The threatened status of humpback whales also provided impetus for the designation of the 1, square-mile Hawaiian Islands Humpback Whale National Marine Sanctuary in to protect humpback whales and their habitat [ ]. This species has shown a tremendous population recovery despite years of overexploitation for their fur, meat, and oil , indiscriminate killing, and decades of habitat degradation, ship strikes, and fishery interactions [ ]. Abundance estimates of the Western DPS declined from , to , individuals between and in rookeries and haul-outs across Southwest Alaska [ ].

Population abundance stabilized in the early s [ , ] with the lowest population estimate in [ ]. Notably, population abundance significantly increased at 2.

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Conservation efforts under both the ESA and the MMPA such as designation of protective zones, critical habitat designation, fishery regulations for prey species, and local regulations around major rookeries and haul-outs have likely contributed to the population recovery success [ ]. NMFS implemented several fishery management measures e. These regulations, designed to reduce competition for prey between commercial fishing and Steller sea lions and increase prey availability, are thought to have contributed to increased prey abundance and a rebound of the DPS [ , ].

In fact, counts have increased at an average of 2. The species has been increasing exponentially and has become one of the largest nesting aggregations in the western Atlantic in recent years [ 42 ]. Historically exploited across the Caribbean [ 54 ], this species has shown a high recovery potential when nesting areas are strictly protected from human disturbance and development, and fishery bycatch is substantially reduced [ 42 ]. The nesting population of green turtles across Florida showed high records of nest numbers in 36, nests and 37, nests compared with only 62 nests estimated in Fig 4.

These record numbers have occurred despite large annual fluctuations in nesting numbers that have been linked to changes in food supply seagrass and macroalgae production due to environmental changes [ ]. In , NMFS and USFWS reclassified green sea turtles into 11 DPSs of which the Florida nesting population was downlisted from endangered to threatened due to strong population growth and record numbers of nests in nesting beaches throughout the peninsula [ ].

However, these population numbers are based on assessing the female component of the population and do not account for males and recruitment of juveniles. ESA protections and several local and international conservation efforts have been important for the recovery of green sea turtles in the North Atlantic and other regions.

ESA regulations have led to fishing gear modifications, major changes in fishing practices, time and area closures, and the establishment of turtle excluder devices for shrimp trawlers [ 87 , ]. The ESA and other state-level laws prohibited direct harvesting of adult turtles and turtle eggs, preventing removal of mature and reproductive adults [ 42 ].

In addition, several national wildlife refuges were dedicated to protecting nesting areas on the Atlantic coast and Gulf of Mexico, with nest watchers and patrols during nesting seasons [ 42 ]. Federal agencies NMFS and USFWS along with state agencies and other institutions have worked together in implementing the management actions in the recovery plan, eliminating or reducing threats in nesting and foraging areas [ 42 ]. Recovery is occurring for representative populations of most marine mammal and sea turtle species listed under the ESA and analyzed in our study.

Representative populations from species listed for over 20 years were more likely to have populations that significantly increased in numbers. In contrast, relatively recently listed species were more likely to have populations with non-significant change or declines. These findings provide critical information to set real-world expectations for recovery of marine mammal and sea turtle populations.

Targeted conservation efforts triggered by ESA listing and other national and international conservation efforts have been largely successful in promoting population recovery leading to the delisting of some species and to significant increases in most others. In general, listed species with designated critical habitat, sufficient conservation funding, and well-implemented species-specific recovery plans tend to recover relatively faster [ 16 , 23 , 24 ].

Our analysis not only underscores the capacity of marine mammal and sea turtle populations to rebound after decades of exploitation and habitat degradation, but also highlights the success of marine species conservation through a combination of ESA protection and other conservation efforts. Several staff from the Center for Biological Diversity gathered and organized the data used in this paper. Thanks to the thorough review by Miyoko Sakashita that substantially improved this paper.


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  5. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract The U. Funding: The authors received no specific funding for this work. Download: PPT. Table 1. Status of marine mammal and sea turtle populations protected under the ESA included in the analysis. Data compilation and availability We collected information and population-level abundance estimates for ESA-listed marine mammal and sea turtle species from published papers and government reports. Population trends and magnitude of change For each marine mammal and sea turtle representative population, we calculated the population trend as percentage change per year and the magnitude of population change as percentage change after ESA listing based on the predicted distributions from the best and final fitted generalized linear or non-linear models Table 2 and S2 Table.

    Table 2. Linear model and ANOVA results of the relationship between time since ESA listing and population trends increasing, non-significant, decreasing for marine mammal and sea turtle populations. Data analysis: Population trajectories and model selection To assess population trajectories after listing we used several types of models including linear models lm , generalized linear models glm , generalized least square models gls , or generalized additive models gam in which population abundance estimates were modeled by running time in years S2 Table.

    Results Status of ESA-listed marine mammal and sea turtle species Protection status for 10 out of the 31 representative populations analyzed in our study changed since they were first listed, with eight of the 10 improving in status. Fig 1. Number and percentage of marine mammal and sea turtle populations protected under the ESA that significantly increased inc , non-significantly change nsc , and significantly decreased dec after listing.

    Fig 2. Population-level trends of cetacean marine mammals listed under the ESA. Fig 3. Population-level trends of non-cetacean marine mammals listed under the ESA. Table 3. Trends and magnitude of change of selected marine mammal and sea turtle populations protected under the ESA. Fig 4.


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    5. Population-level trajectories of sea turtles listed under the ESA. Discussion Most representative populations of marine mammal and sea turtle species protected under the ESA that met our selection criteria significantly increased after listing, indicating population recoveries. Western DPS of Steller sea lion. North Atlantic DPS of green sea turtle. Conclusions Recovery is occurring for representative populations of most marine mammal and sea turtle species listed under the ESA and analyzed in our study.

      Supporting information. S1 Table. Status of marine mammal and sea turtle species protected under the ESA excluded in the analyses. S2 Table. Final model parameters used to determine location-specific population trends. S1 Fig. Approximate geographic distribution of cetacean marine mammal populations analyzed in our study.