Ageing live New Zealand sea lions (Phocarctos hookeri) using the first post-canine tooth

2004 ◽  
Vol 31 (2) ◽  
pp. 177 ◽  
Author(s):  
S. Childerhouse ◽  
G. Dickie ◽  
G. Hessel
Keyword(s):  
New Zealand ◽  
Age Estimation ◽  
Growth Layer ◽  
Canine Tooth ◽  
Sea Lions ◽  
Glass Slides ◽  
Significant Difference ◽  
Layer Groups ◽  
Phocarctos Hookeri ◽  
Age Estimates

Live New Zealand sea lions (Phocarctos hookeri) were aged from growth layer groups (GLGs) in the cementum of a lower first post-canine tooth. A single post-canine (PC1) was removed from individuals of known-age (n = 74) between 1997 and 2001 while under a full anaesthetic. Teeth were decalcified, sectioned on a cryostat, stained and then mounted on glass slides. Age was estimated by counting GLGs in the cementum multiple times. Age estimates were calibrated with known-aged individuals and confirmed the annual formation of cementum annuli in PC1 tooth. While there is some variation in assigning exact age to individuals, it was possible to age 94% of teeth to the exact year or to within 1 year of actual age. There was no significant difference in the slope of regression lines associated with actual and estimated age using this technique (t-test, t = 0.309, d.f. = 144, P < 0.05). Accuracy in ageing was improved by discarding sets of readings with low precision and re-reading the tooth until a precise set of estimates was made. GLGs in the cementum were more accurate and robust for age estimation than using GLGs in the dentine. This paper describes a reliable method for the preparation and ageing of the first post-canine tooth (PC1) from live New Zealand sea lions.

scholarly journals Accuracy, precision, and error in age estimation of Florida manatees using growth layer groups in earbones

2019 ◽  
Vol 100 (4) ◽  
pp. 1350-1363 ◽  
Author(s):  
Gina L Lonati ◽  
Amber R Howell ◽  
Jeffrey A Hostetler ◽  
Paul Schueller ◽  
Martine de Wit ◽  
...  
Keyword(s):  
Age Estimation ◽  
Wildlife Conservation ◽  
Absolute Error ◽  
Large Sample Size ◽  
Growth Layer ◽  
Florida Manatee ◽  
Data Set ◽  
Photo Identification ◽  
Layer Groups ◽  
Age Estimates

AbstractAges of Florida manatees (Trichechus manatus latirostris) can be estimated by counting annual growth layer groups (GLGs) in the periotic dome portion of the tympanoperiotic complex of their earbones. The Florida Fish and Wildlife Conservation Commission manages an archive of more than 8,700 Florida manatee earbones collected from salvaged carcasses from 1989 to 2017. Our goal was to comprehensively evaluate techniques used to estimate age, given this large sample size and changes to processing protocols and earbone readers over time. We developed new standards for estimating ages from earbones, involving two independent readers to obtain measurements of within- and between-reader precision. To quantify accuracy, precision, and error, 111 earbones from manatees with approximately known ages (first known as calves: “KAC”) and 69 earbones from manatees with minimum known ages (“MKA,” based on photo-identification sighting histories) were processed, and their ages were estimated. There was greater precision within readers (coefficient of variation, CV: 2.4–8.5%) than between readers (CV: 13.1–13.3%). The median of age estimates fell within the true age range for 63.1% of KAC cases and was at least the sighting duration for 75.0% of MKA cases. Age estimates were generally unbiased, as indicated by an average raw error ± SD of −0.05 ± 3.05 years for the KAC group. The absolute error (i.e., absolute value of raw error) of the KAC data set averaged 1.75 ± 2.50 years. Accuracy decreased and error increased with increasing known age, especially for animals over 15 years old, whose ages were mostly underestimated due to increasing levels of resorption (the process of bone turnover that obscures GLGs). Understanding the degree of uncertainty in age estimates will help us assess the utility of age data in manatee population models. We emphasize the importance of standardizing and routinely reviewing age estimation and processing protocols to ensure that age data remain consistent and reliable.

scholarly journals Inter-lab comparison of precision and recommended methods for age estimation of Florida manatee (Trichechus manatus latirostris) using growth layer groups in earbones

2016 ◽  
Vol 8 ◽  
Author(s):  
Katherine Brill ◽  
Miriam Marmontel ◽  
Meghan Bolen-Richardson ◽  
Robert EA Stewart
Keyword(s):  
Age Estimation ◽  
Effective Management ◽  
Growth Layer ◽  
Florida Manatee ◽  
Trichechus Manatus ◽  
Trichechus Manatus Latirostris ◽  
Apparent Source ◽  
Layer Groups ◽  
Age Estimates ◽  
Good Agreement

Manatees are routinely aged by counting Growth Layer Groups (GLGs) in periotic bones (earbones). Manatee carcasses recovered in Florida between 1974 and 2010 provided age-estimation material for three readers and formed the base for a retrospective analysis of aging precision (repeatability). All readers were in good agreement (high precision) with the greatest apparent source of variation being the result of earbone remodelling with increasing manatee age. Over the same period, methods of sample preparation and of determining a final age estimate changed. We examined the effects of altering methods on ease of reading GLGs and found no statistical differences. Accurate age estimates are an important component for effective management of the species and for better models of population trends and we summarize the currently recommended methods for estimating manatee ages using earbones. 

scholarly journals NEONATAL MORTALITY IN NEW ZEALAND SEA LIONS (PHOCARCTOS HOOKERI ) AT SANDY BAY, ENDERBY ISLAND, AUCKLAND ISLANDS FROM 1998 TO 2005

2007 ◽  
Vol 43 (3) ◽  
pp. 461-474 ◽  
Author(s):  
A. Castinel ◽  
P. J. Duignan ◽  
W. E. Pomroy ◽  
N. López-Villalobos ◽  
N. J. Gibbs ◽  
...  
Keyword(s):  
New Zealand ◽  
Neonatal Mortality ◽  
Sea Lions ◽  
Phocarctos Hookeri

scholarly journals Pathology and Epidemiology of Stillbirth in New Zealand Sea Lions (Phocarctos hookeri) From Enderby Island, Auckland Islands, 1998–2012

2016 ◽  
Vol 53 (6) ◽  
pp. 1241-1247 ◽  
Author(s):  
S. A. Michael ◽  
B. L. Chilvers ◽  
S. A. Hunter ◽  
P. Duignan ◽  
W. Roe
Keyword(s):  
New Zealand ◽  
Sea Lions ◽  
Phocarctos Hookeri

Foraging energetics and diving behavior of lactating New Zealand sea lions, Phocarctos hookeri

2000 ◽  
Vol 203 (23) ◽  
pp. 3655-3665 ◽  
Author(s):  
D.P. Costa ◽  
N.J. Gales
Keyword(s):  
New Zealand ◽  
Metabolic Rate ◽  
Dive Depth ◽  
Diving Behavior ◽  
Metabolic Rates ◽  
Sea Lion ◽  
Water Turnover ◽  
Sea Lions ◽  
The Mean ◽  
Phocarctos Hookeri

The New Zealand sea lion, Phocarctos hookeri, is the deepest- and longest-diving sea lion. We were interested in whether the diving ability of this animal was related to changes in its at-sea and diving metabolic rates. We measured the metabolic rate, water turnover and diving behavior of 12 lactating New Zealand sea lions at Sandy Bay, Enderby Island, Auckland Islands Group, New Zealand (50 degrees 30′S, 166 degrees 17′E), during January and February 1997 when their pups were between 1 and 2 months old. Metabolic rate (rate of CO(2) production) and water turnover were measured using the (18)O doubly-labeled water technique, and diving behavior was measured with time/depth recorders (TDRs). Mean total body water was 66.0+/−1.1 % (mean +/− s.d.) and mean rate of CO(2) production was 0. 835+/−0.114 ml g(−)(1)h(−)(1), which provides an estimated mass-specific field metabolic rate (FMR) of 5.47+/−0.75 W kg(−)(1). After correction for time on shore, the at-sea FMR was estimated to be 6.65+/−1.09 W kg(−)(1), a value 5.8 times the predicted standard metabolic rate of a terrestrial animal of equal size. The mean maximum dive depth was 353+/−164 m, with a mean diving depth of 124+/−36 m. The mean maximum dive duration was 8.3+/−1.7 min, with an average duration of 3.4+/−0.6 min. The deepest, 550 m, and longest, 11.5 min, dives were made by the largest animal (155 kg). Our results indicate that the deep and long-duration diving ability of New Zealand sea lions is not due to a decreased diving metabolic rate. Individual sea lions that performed deeper dives had lower FMRs, which may result from the use of energetically efficient burst-and-glide locomotion. There are differences in the foraging patterns of deep and shallow divers that may reflect differences in surface swimming, time spent on the surface and/or diet. Our data indicate that, although New Zealand sea lions have increased their O(2) storage capacity, they do not, or cannot, significantly reduce their at-sea metabolic rates and are therefore likely to be operating near their physiological maximum.

Philopatry and site fidelity of New Zealand sea lions (Phocarctos hookeri)

2008 ◽  
Vol 35 (5) ◽  
pp. 463 ◽  
Author(s):  
B. Louise Chilvers ◽  
Ian S. Wilkinson
Keyword(s):  
New Zealand ◽  
Site Fidelity ◽  
Breeding Area ◽  
Quantitative Investigation ◽  
Sea Lion ◽  
Breeding Sites ◽  
Auckland Island ◽  
Sea Lions ◽  
Breeding Habitats ◽  
Phocarctos Hookeri

The New Zealand sea lion (NZ sea lion), Phocarctos hookeri, is New Zealand’s only endemic pinniped, and one of the worlds rarest otariids. It is classified as ‘Threatened’ based primarily on the low number of breeding sites and restricted distribution. In New Zealand, a species listed as ‘threatened’ is required to be managed to allow its recovery and removal from the list within 20 years. For NZ sea lions this is dependant on the establishment of new breeding areas. However, understanding the recolonisation processes for pinnipeds is still in its infancy with factors such as philopatry needing more research to understand individual dispersal and the recolonisation process. This paper presents the first quantitative investigation into the level of site fidelity and philopatry to breeding beaches in NZ sea lions. Data from resights of NZ sea lions marked as pups from the northern Auckland Island breeding area suggest that both site fidelity and philopatry are important characteristics of this species. Our results show that overall: (1) females have a higher resighting rate than males, particularly at natal sites; (2) female non-natal resightings are predominantly restricted to locations within the northern Auckland Island breeding area (an area of ~10 km2), whereas male resightings are more widely dispersed (up to 700 km to NZ mainland); and (3) philopatry occurs for both sexes, but is more predominant in females than males, with males displaying delay related to sexual and social maturity. The colonisation of new breeding habitats rarely occurs when philopatry is strong and population density is low, stable or declining such as seen for NZ sea lions. Therefore, this research indicates that management of NZ sea lions needs to minimise anthropogenic mortality and encourage population growth to maximise density at breeding sites and encourage females to disperse to establish new breeding areas.

scholarly journals Pup mortality in New Zealand sea lions (Phocarctos hookeri) at Enderby Island, Auckland Islands, 2013-18

PLoS ONE ◽  
2019 ◽  
Vol 14 (11) ◽  
pp. e0225461
Author(s):  
Sarah A. Michael ◽  
David T. S. Hayman ◽  
Rachael Gray ◽  
Ji Zhang ◽  
Lynn Rogers ◽  
...  
Keyword(s):  
New Zealand ◽  
Sea Lions ◽  
Pup Mortality ◽  
Phocarctos Hookeri

scholarly journals Interannual and individual variation in milk composition of New Zealand sea lions (Phocarctos hookeri)

2012 ◽  
Vol 93 (4) ◽  
pp. 1006-1016 ◽  
Author(s):  
Federico G. Riet-Sapriza ◽  
PÁdraig J. Duignan ◽  
B. Louise Chilvers ◽  
Ian S. Wilkinson ◽  
Nicolás Lopez-Villalobos ◽  
...  
Keyword(s):  
New Zealand ◽  
Individual Variation ◽  
Milk Composition ◽  
Sea Lions ◽  
Phocarctos Hookeri

scholarly journals Historical population size of the threatened New Zealand sea lion Phocarctos hookeri

2015 ◽  
Vol 97 (2) ◽  
pp. 436-443 ◽  
Author(s):  
Catherine J. Collins ◽  
B. Louise Chilvers ◽  
Matthew Taylor ◽  
Bruce C. Robertson
Keyword(s):  
New Zealand ◽  
Population Size ◽  
Effective Population Size ◽  
Carrying Capacity ◽  
Effective Population ◽  
Sea Lion ◽  
Sea Lions ◽  
Target Values ◽  
Phocarctos Hookeri

Abstract Marine mammal species were exploited worldwide during periods of commercial sealing in the 18th and 19th centuries. For many of these species, an estimate of the pre-exploitation abundance of the species is lacking, as historical catch records are generally scarce and inaccurate. Genetic estimates of long-term effective population size provide a means to estimate the pre-exploitation abundance. Here, we apply genetic methods to estimate the long-term effective population size of the subantarctic lineage of the New Zealand sea lion (NZ sea lion), Phocarctos hookeri . This species is predominantly restricted to the subantarctic islands, south of mainland New Zealand, following commercial sealing in the 19th century. Today, the population consists of ~9,880 animals and population growth is slow. Auckland Island breeding colonies of NZ sea lion are currently impacted by commercial trawl fisheries via regular sea lion deaths as bycatch. In order to estimate sustainable levels of bycatch, an estimate of the population’s carrying capacity ( K ) is required. We apply the genetically estimated long-term effective population size of NZ sea lions as a proxy for the estimated historical carrying capacity of the subantarctic population. The historical abundance of subantarctic NZ sea lions was significantly higher than the target values of K employed by the contemporary management. The current management strategy may allow unsustainable bycatch levels, thereby limiting the recovery of the NZ sea lion population toward historical carrying capacity.

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