Susan J Chivers

Susan J Chivers
National Oceanic and Atmospheric Administration | NOAA

Doctor of Philosophy

About

94
Publications
20,972
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2,558
Citations
Citations since 2017
12 Research Items
1270 Citations
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2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200

Publications

Publications (94)
Article
Understanding the effect of stage‐specific traits on species feeding habits can reveal how natural selection shapes life strategies. Amino acid (AA) nitrogen stable isotopes (δ15N) provide multiple proxies of habitat baseline values and diet that can improve our understanding of species feeding strategies relative to their animal metabolism. We eva...
Article
Full-text available
Distance sampling is a popular statistical method to estimate the density of wild animal populations. Conventional distance sampling represents animals as fixed points in space that are detected with an unknown probability that depends on the distance between the observer and the animal. Animal movement can cause substantial bias in density estimat...
Article
Most mammals exhibit natal dispersal of one or both sexes, a behavior that likely evolved in part to reduce the chances of breeding with close relatives. When natal social group fidelity of both sexes has been documented, the risk of inbreeding is reduced by breeding among rather than within social groups. We investigated mating patterns in an enda...
Article
Four geographic forms of spinner dolphin (Stenella longirostris) occur in the eastern tropical Pacific. Two of the forms are pelagic: the eastern and whitebelly, and two are coastal: the Central American and Tres Marias spinner dolphins. Of these, only the Tres Marias form lacks recognition appropriate for developing management and conservation pla...
Article
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The dermis of cetaceans is in constant contact with microbial species. Although the skin of the bottlenose dolphin provides adequate defense against most disease-causing microbes, it also provides an environment for microbial community development. Microbial community uniqueness and richness associated with bottlenose dolphin skin is a function of...
Article
Stable isotope analysis (SIA) has rapidly become a useful tool to study the ecology of wild animal populations, especially for elusive, wide-ranging predators like marine mammals. The development of projectile biopsy techniques resulted in the collection of thousands of cetacean tissue samples that were archived in a dimethyl sulfoxide (DMSO) solut...
Article
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Climate variability alters nitrogen cycling, primary productivity, and dissolved oxygen concentration in marine ecosystems. We examined the role of this variability (as measured by six variables) on food chain length (FCL) in the California Current (CC) by reconstructing a time series of amino acid–specific δ¹⁵N values derived from common dolphins,...
Book
The diversity of mammals in San Diego County is greater than any other county in the United States, yet there has been no synthesis of their identification, distribution, natural history, or the conservation challenges they face—until now. The new San Diego County Mammal Atlas will serve as the definitive guide to the mammals of San Diego County....
Article
Several recent oil spills in the United States have had the potential to impact large numbers and multiple populations of cetaceans (whales and dolphins) and pinnipeds (seals and sea lions), namely the Macondo-252/Deepwater Horizon oil spill from April 2010, the Texas City Y event in March 2014, and the Refugio Beach oil spill in May 2015. In each...
Article
Recovery of cetacean carcasses provides data on levels of human-caused mortality, but represents only a minimum count of impacts. Counts of stranded carcasses are negatively biased by factors that include at-sea scavenging, sinking, drift away from land, stranding in locations where detection is unlikely, and natural removal from beaches due to wav...
Article
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Non-targeted GC×GC-TOF/MS analysis of blubber from 8 common bottlenose dolphins (Tursiops truncatus) inhabiting the Southern California Bight was performed to identify novel, bioaccumulative DDT-related compounds, and to determine their abundance relative to the commonly-studied DDT-related compounds. We identified 45 bioaccumulative DDT-related co...
Article
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The role of ecological and changing environmental factors in the radiation of species diversity is a fundamental question in evolutionary biology. Of particular interest is the potential for these factors to determine the boundary between what we would consider differentiation among populations and incipient speciation. Dolphins in the genus Delphi...
Article
Reproductive parameters were estimated and compared for eastern North Pacific populations of common dolphins using specimen and photogrammetric data. Age and length data for Delphinus capensis and D. delphis specimens recovered as bycatch or strandings were used to estimate the postnatal growth rates needed to estimate age for calves measured in ae...
Article
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Correlations between morphological and genetic data provide evidence to delineate species or evolutionarily significant units, which then become the units to conserve in management plans. Here, we examine the distribution and genetic differentiation of two morphotypes of short-finned pilot whale (Globicephala macrorhynchus) in the Pacific Ocean. Mi...
Article
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Species distribution models are now widely used in conservation and management to predict suitable habitat for protected marine species. The primary sources of dynamic habitat data have been in situ and remotely sensed oceanic variables (both are considered "measured data"), but now ocean models can provide historical estimates and forecast predict...
Article
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We inferred the population densities of blue whales (Balaenoptera musculus) and short-beaked common dolphins (Delphinus delphis) in the Northeast Pacific Ocean as functions of the water-column’s physical structure by implementing hierarchical models in a Bayesian framework. This approach allowed us to propagate the uncertainty of the field observat...
Article
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When paired with dart biopsying, quantifying cortisol in blubber tissue may provide an index of relative stress levels (i.e., activation of the hypothalamus-pituitary-adrenal axis) in free-ranging cetacean populations while minimizing the effects of the act of sampling. To validate this approach, cortisol was extracted from blubber samples collecte...
Article
Targeted environmental monitoring reveals contamination by known chemicals, but may exclude potentially pervasive but unknown compounds. Marine mammals are sentinels of persistent and bioaccumulative contaminants due to their longevity and high trophic position. Using nontargeted analysis, we constructed a mass spectral library of 327 persistent an...
Conference Paper
Background/Question/Methods In marine ecosystems, climate change is altering biochemical cycling, the distribution of species and food web structure, but it is unknown the magnitude of such changes. In recent decades, the highly productive California Current System has experienced increasing frequencies of El Niño-Southern Oscillation (ENSO) even...
Article
Full-text available
Blubber progesterone levels were measured in biopsy samples and used to predict the pregnancy status of 507 female common dolphins (204 long-beaked common dolphins, Delphinus capensis, and 303 short-beaked common dolphins, D. delphis). Samples were collected in the coastal waters of the eastern North Pacific between central California, USA and the...
Article
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False killer whales (Pseudorca crassidens) are large delphinids typically found in deep water far offshore. However, in the Hawaiian Archipelago, there are 2 resident island-associated populations of false killer whales, one in the waters around the main Hawaiian Islands (MHI) and one in the waters around the Northwestern Hawaiian Islands (NWHI). W...
Data
##Assembly-Data-START## Assembly Method :: SEQED v. 1.0.3; Sequencher v. 4.1; Sequencher v. 4.8 Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
##Assembly-Data-START## Assembly Method :: SEQED v. 1.0.3; Sequencher v. 4.1; Sequencher v. 4.8 Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
##Assembly-Data-START## Assembly Method :: SEQED v. 1.0.3; Sequencher v. 4.1; Sequencher v. 4.8 Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Article
We present genetic and morphological evidence supporting the recognition of a previously synonymized species of Mesoplodon beaked whale in the tropical Indo-Pacific, Mesoplodon hotaula. Although the new species is closely-related to the rare ginkgo-toothed beaked whale M. ginkgodens, we show that these two lineages can be differentiated by maternal...
Article
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The northeastern offshore population of the pantropical spotted dolphin (Stenella attenuata) in the eastern tropical Pacific remains listed as depleted under the Marine Mammal Protection Act, and recent estimates of abundance show that recovery has been slow. One hypothesis for the slow recovery is that continued chase and encirclement by the tuna...
Article
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Molecular assays were used to determine the sex of 1,294 biopsied common dolphins (658 long-beaked common dolphins, Delphinus capensis, and 636 short-beaked common dolphins, D. delphis) in the Southern California Bight. Sex ratio differed substantially between the two species; females comprised 241 (36.6%) of D. capensis samples and 410 (64.5%) of...
Article
Marine spatial planning provides a comprehensive framework for managing multiple uses of the marine environment and has the potential to minimize environmental impacts and reduce conflicts among users. Spatially explicit assessments of the risks to key marine species from human activities are a requirement of marine spatial planning. We assessed th...
Article
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The association of yellowfin tuna and pantropical spotted dolphins in the eastern tropical Pacific Ocean (ETP) has been exploited by tuna fishermen and has intrigued scientists for decades, yet we still have questions about what the benefits of the association are-whether the association is obligatory or facultative, why the tuna are most often fou...
Article
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We present genetic and morphological data supporting the recognition of a previously described but unrecognised Mesoplodon beaked whale in the tropical Indo-Pacific. Currently known from at least seven specimens (Sri Lanka [1], Kiribati [1+], Hawai’i [3], Maldives [1], Seychelles [1]), this beaked whale is the sister-taxon to M. ginkgodens proper....
Article
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The abundance of the long-beaked common dolphin (Delphinus capensis) is estimated from data collected during a 2009 ship-based line-transect survey. The survey was designed to provide fine-scale coverage of the known range of D. capensis along the California and west Baja California coasts. Estimates of D. capensis abundance presented are the highe...
Article
Hematology, serum chemistry, and plasma hormones were evaluated in 72 pantropical spotted dolphins (Stenella attenuata attenuata) from the eastern tropical Pacific in an attempt to define the degree of stress associated with chase and encirclement by a tuna purse seiner, and are here reported for the first time for this species. Dolphins had high l...
Technical Report
The “Ecosystem Survey of Delphinus Species” research survey focused on the two species of common dolphin, Delphinus delphis and D. capensis, found off southern California, USA, and Baja California, Mexico. The primary objective was to provide information to improve conservation and management plans for these species. The project used a multidiscipl...
Article
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For the past half-century, the purse seine fishery for yellowfin tuna has been a significant factor in the lives of dolphins in the eastern tropical Pacific (ETP). However, little is known about how frequently an individual dolphin is exposed to the fishery, and there are no methods available for accurately assessing the prior exposure of dolphins...
Article
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Genetic structure and phylogeography of the harbour porpoise Phocoena phocoena in the North Pacific were examined using 358bps sequences from the 5′ end of the mitochondrial DNA control region including those reported previously and newly obtained from the west Pacific. AMOVA and pairwise population φ st estimates clearly revealed genetic differen...
Article
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There were 717 cetacean strandings recorded in San Diego County, California, USA between 1851 and 2008. These strandings comprised 18 odontocete and 6 mysticete species. Common dolphins (both the short-beaked (Delphinus delphis) and long-beaked common dolphin (D. capensis)) were the most commonly stranded cetacean species (43.2%), followed by bottl...
Chapter
Full-text available
A species' life-history strategy is defined by parameters that describe how individuals allocate resources to growth, reproduction, and survival. Among cetacean species, the life-history strategies are diverse and differ markedly between the two cetacean suborders: the baleen whales (suborder Mysticeti) and the toothed whales (suborder Odontoceti)....
Article
: Persistent organic pollutants (POPs) have been measured in tissues of marine mammals since the mid 1960s (Holden and Marsden, 1967; Wolman and Wilson, 1970). These compounds include several pesticides (e.g., DDTs, chlordanes) and industrial chemicals (e.g., PCBs) that are ubiquitous, highly lipophilic and not readily degraded or metabolized. As a...
Article
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AbstractA novel molecular technique was used to measure blubber testosterone (BT) in 114 male short-beaked common dolphins, Delphinus delphis, collected from incidental fishery bycatch and strandings. When these concentrations were compared across maturity states, the mean (± SEM) BT levels of mature D. delphis (14.3 ± 3.0 ng/g) were significantly...
Article
Life-history parameters are estimated for two forms of the spinner dolphin (Stenella longirostris (Gray, 1828)): the eastern subspecies (Stenella longirostris orientalis Perrin, 1990) and the whitebelly hybrid. The data analyzed (n = 3138 eastern and 3099 whitebelly spinner dolphins) were collected between 1968 and 1994 from female dolphins inciden...
Article
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We radio tracked 20 pantropical spotted dolphins (Stenella attenuata) in the pelagic waters of the eastern tropical Pacific Ocean during three research cruises in 1992, 1993, and 2001. Dolphins were tracked for up to 6 d from 20 to 1,000 km offshore. Seventeen of these dolphins also carried time–depth recorders, nine of which were recovered with a...
Article
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Age was estimated from teeth for 1,267 female eastern spinner dolphins (Stenella longirostris orientalis) and 1,071 female whitebelly spinner dolphins (S. longirostris) incidentally killed in the eastern tropical Pacific yellowfin tuna purse-seine fishery between 1973 and 1982. The final age assigned to each specimen was the mean of two readers' ag...
Article
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Abstract—There is little knowledge of the impact of illegal, 17 unregulated and unreported (IUU) fishing on marine megafauna such as,18 whales, dolphins and porpoises, especially in the tropical Indo-Pacific 19 where this problem is rife. Here we present the results from the DNA,20 identification of a rare beaked whale (Mesoplodon ginkgodens),21 co...
Article
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False killer whales (Pseudorca crassidens (Owen, 1846)) are incidentally taken in the North Pacific pelagic long-line fishery, but little is known about their population structure to assess the impact of these takes. Using mitochondrial DNA (mtDNA) control region sequence data, we quantified genetic variation for the species and tested for genetic...
Article
Full-text available
We characterize the life-history strategy of female short-beaked common dolphins (Delphinus delphis L., 1758) inhabiting the eastern tropical Pacific by estimating several growth and reproductive parameters. Reproductive condition (n = 700) and age (n = 405) were determined for animals sampled from those incidentally killed in the yellowfin tuna (T...
Article
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We estimated generation length and percent mature for 58 cetacean species to assess their status using criteria developed by the IUCN. We first reviewed the literature and types of data available and then developed a set of simple rules to ensure consistent use of the best available data to estimate these parameters. The method we developed estimat...
Article
Full-text available
Spatial and temporal variability in mean age, breeding season and mean body length were examined for female short-beaked common dolphins Delphinus delphis in the eastern tropical Pacific (ETP). Specimens were obtained from central stock D. delphis incidentally killed in the tuna purse-seine fishery between 1973 and 1993. To examine spatial variabil...
Article
Concordance between mitochondrial DNA (mtDNA) markers and morphologically based species identifications was examined for the two currently recognized Kogia species. We sequenced 406 base pairs of the control region and 398 base pairs of the cytochrome b gene from 108 Kogia breviceps and 47 K. sima samples. As expecred, the two sister species were r...
Article
We estimated the total number of pantropical spotted dolphin (Stenella attenuata) mothers killed without their calves ("calf deficit") in all tuna purse-seine sets from 1973-90 and 1996-2000 in the eastern tropical Pacific. Estimates were based on a tally of the mothers killed as reported by color pattern and gender, several color-pattern-based fre...
Article
Full-text available
Age was estimated for 1,318 female eastern spinner dolphins (Stenella longirostris orientalis). Samples were collected from dolphins incidentally killed in the eastern tropical Pacific tuna purse-seine fishery between 1970 and 1982. In this report I present the age frequency distribution of this data set. The maximum age observed was 26. Preliminar...
Article
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A suite of complementary stress studies was conducted August-October 2001 to investigate potential effects of repeated chase and encirclement on northeastern offshore spotted dolphins (Stenella attenuata attenuata) and eastern spinner dolphins (Stenella longirostris orientalis). The studies were conducted as part of a larger research program mandat...
Article
Using estimates of age made for a sample of 1,106 pantropical spotted dolphins (Stenella attenuata attenuata) belonging to the northeastern stock, we generated age frequency distributions for the observed kill of this stock. The aged sample was a subset of the biological samples collected from spotted dolphins incidentally killed in the fishery bet...
Article
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During the 2001 Chase Encirclement Stress Studies (CHESS) cruise, 9 pantropical spotted dolphins (Stenella attenuata) were radio tagged and tracked and 6 spotted dolphins were satellite tagged and tracked. The dolphins tracked with VHF radio tags also carried time-depth recorders (TDRs) (n=3), time-depth-velocity recorders (TDVRs) (n=4) or time-dep...
Article
Full-text available
Concern about the conservation and management of harbour porpoise (Phocoena phocoena) populations, which have experienced relatively large incidental fishery kills in localised areas throughout their range, has prompted research to better understand their population structure. Both mitochondrial and nuclear (microsatellites) DNA were used to examin...
Article
Full-text available
In October 1997 we observed a herd of approximately 35 killer whales (Orcinus orca) attack a pod of nine sperm whales (Physeter macrocephalus) 130 km off the coast of central California. During the four hours we watched, adult female killer whales, including some with calves, attacked in waves of four to five animals in what was apparently a “wound...
Article
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We estimate abundance and describe the depth distribution of harbor porpoise (Phocoena phocoena) in northern California from a November 1995 ship survey. This was the first ship survey designed to systematically survey different depth strata out to 91 m (50 fathoms) in this region. Harbor porpoise abundance in northern California is estimated at 56...
Article
Using genetic data to estimate dispersal is attractive because direct estimation is often infeasible. Unfortunately, analytical tools remain rudimentary. Various standard population genetic formulae estimate dispersal rates between populations but require unrealistic assumptions, such as equal population size. Recent increases in computer speed ena...
Article
Full-text available
Projectile biopsy samples are collected on all Southwest Fisheries Science Center research cruises and used in molecular genetic studies of cetacean species phylogeny, population structure and social behavior. Although we continue to improve our techniques to increase the number of species we can sample, our methodologies were essentially standardi...
Article
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Identified prey of pantropical spotted dolphins, Stenella attenuata, include 56 species of fish and 36 species of cephalopods. Species identifications were made from fish otoliths and cephalopod beaks recovered from 428 stomachs collected throughout the eastern tropical Pacific between 1989 and 1991. The most frequently found fish were lanternfish...
Article
In July 1990, an observer program was established to collect data on the bycatch of the drift and set gillnet fisheries operating off the coast of California. These data are used for estimating mortality and for further studies of the biology of the species impacted. To date. 16 species of Cetacea have been identified in the observed incidental kil...
Article
To evaluate potential biological indices of population status (i.e., N relative to carrying capacity [K]), we tested for correlations between estimates of several life history parameters and status for 3 dolphin species in the eastern tropical Pacific between 1974 and 1992. On the basis of a qualitative population response model, we predicted that...
Article
The observed kill is summarised by species for 43 US tuna purse-seine vessel-trips and 796 California gillnet vessel-trips made during 1992. There were 431 cetaceans observed killed incidentally in the US tuna fishery and 88 cetaceans in the drift- and set-net fisheries operating off the coast of California. Life history data were collected for 40%...