Wildlife research often requires marking and tagging animals to collect data on survival, reproduction, movement, behaviour and physiology. Identification of individual marine mammals can be carried out using tags, brands, paint, dye, photogrammetry, telemetry and other techniques. An analysis of peer-reviewed articles published from January 1980 to April 2011 addressing the effects of marking revealed a preponderance of studies focussed on short-term effects such as injuries and behavioural changes. Some marking techniques were reported to cause pain and to change swimming and haul-out behaviour, maternal attendance, and duration of foraging trips. However, marking has typically not been found to affect survival. No published research has addressed other possible long-term effects of marking related to injuries or pain responses. Studies of the more immediate effects of marking (mostly related to externally attached devices such as radio-transmitters) have shown a variety of different types and magnitudes of responses. It is important to note that studies failing to find treament differences are less likely to be published, meaning that the present and any other reviews based on published literature may be a biased sample of all research conducted on the topic. Publishing results that found no or low impacts (i.e. best practices) as well as those that found significant impacts on animals should both be encouraged. Future research under more controlled conditions is required to document acute effects of marking, including injury and pain, and to better understand longer-term effects on health, reproduction and survival. We recommend that studies using marked animals standardise their reports, with added detail on methodology, monitoring and sampling design, and address practices used to minimise the impact of marking on marine mammals.

https://bioone.org/journals/wildlife-research/volume-39/issue-1/WR10177/A-review-of-the-effects-of-different-marking-and-tagging/10.1071/WR10177.pdf

A review of the effects of different marking and tagging techniques on marine mammals

Offspring size affects survival and subsequent reproduction in many organisms. However, studies of offspring size in large mammals are often limited to effects on juveniles because of the difficulty of following individuals to maturity. We used data from a long-term study of individually marked gray seals (Halichoerus grypus; Fabricius, 1791) to test the hypothesis that larger offspring have higher survival to recruitment and are larger and more successful primiparous mothers than smaller offspring. Between 1998 and 2002, 1182 newly weaned female pups were branded with unique permanent marks on Sable Island, Canada. Each year through 2012, all branded females returning to the breeding colony were identified in weekly censuses and a subset were captured and measured. Females that survived were significantly longer offspring than those not sighted, indicating size-selective mortality between weaning and recruitment. The probability of female survival to recruitment varied among cohorts and increased nonlinearly with body mass at weaning. Beyond 51.5 kg (mean population weaning mass) weaning mass did not influence the probability of survival. The probability of female survival to recruitment increased monotonically with body length at weaning. Body length at primiparity was positively related to her body length and mass at weaning. Three-day postpartum mass (proxy for birth mass) of firstborn pups was also positively related to body length of females when they were weaned. However, females that were longer or heavier when they were weaned did not wean heavier firstborn offspring.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.1450

Offspring size at weaning affects survival to recruitment and reproductive performance of primiparous gray seals.

Monitoring free-ranging animals in their natural habitat is a keystone of ecosystem conservation and increasingly important in the context of current rates of loss of biological diversity. Data collected from individuals of endangered species inform conservation policies. Conservation professionals assume that these data are reliable—that the animals from whom data are collected are representative of the species in their physiology, ecology, and behavior and of the populations from which they are drawn. In the last few decades, there has been an enthusiastic adoption of invasive techniques for gathering ecological and conservation data. Although these can provide impressive quantities of data, and apparent insights into animal ranges and distributions, there is increasing evidence that these techniques can result in animal welfare problems, through the wide-ranging physiological effects of acute and chronic stress and through direct or indirect injuries or compromised movement. Much less commonly, however, do conservation scientists consider the issue of how these effects may alter the behavior of individuals to the extent that the data they collect could be unreliable. The emerging literature on the immediate and longer-term effects of capture and handling indicate it can no longer be assumed that a wild animal's survival of the process implies the safety of the procedure, that the procedure is ethical, or the scientific validity of the resulting data. I argue that conservation professionals should routinely assess study populations for negative effects of their monitoring techniques and adopt noninvasive approaches for best outcomes not only for the animals, but also for conservation science.



Efecto de la Tecnica de Monitoreo en la Calidad de la Ciencia de la Conservacion

Resumen

Monitorear animales de libre distribucion en su ambiente natural es clave en la conservacion de ecosistemas y de creciente importancia en el contexto de las tasas actuales de perdida de la diversidad biologica. Los datos colectados de individuos de especies en peligro informan a las politicas de conservacion. Los conservacionistas suponen que estos datos son confiables, es decir que los animales de los cuales los datos son colectados son representativos de la fisiologia, ecologia y el comportamiento de la especie y de todas las poblaciones de donde son tomados. En las ultimas decadas ha habido una adopcion entusiasta de tecnicas invasivas para la colecta de datos ecologicos y de conservacion. Aunque estas pueden proporcionar cantidades impresionantes de datos y supuesta penetracion hacia los rangos y distribucion de los animales hay creciente evidencia de que estas tecnicas pueden resultar en problemas de bienestar animal a traves de los amplios efectos fisiologicos de estres cronico y agudo y por medio de movimiento dificultado o heridas directas o indirectas. Sin embargo, los conservacionistas pocas veces consideran el problema de como estos efectos pueden alterar el comportamiento de los individuos hasta el punto en el que los datos que recopilen sean desconfiables. La literatura reciente sobre los efectos inmediatos y a largo plazo de la captura y el manejo indican que ya no se puede suponer que la supervivencia de un animal silvestre al proceso implica la seguridad del procedimiento, que el procedimiento sea etico o la validez cientifica de los datos resultantes. Yo explico que los conservacionistas deberian evaluar rutinariamente estudios poblaciones para saber si hay efectos negativos de las tecnicas de monitoreo y adoptar aproximaciones no-invasivas para el mejor resultado no solamente para los animales sino tambien para la ciencia de la conservacion.

/pdf/effect-of-monitoring-technique-on-quality-of-conservation-1f73zv4iyi.pdf

Effect of monitoring technique on quality of conservation science.

Mercury is a global contaminant of concern for the fetus and the neonate of piscivores. Methylmercury, produced within marine ecosystems, is of particular concern as a readily absorbed neurotoxicant transported across the blood brain barrier and transplacentally. In the North Pacific Ocean, Steller sea lions are broadly distributed apex predators and, as such, integrate complex food webs and the associated exposure and possible adverse effects of toxic and infectious agents. Hair, including lanugo, was examined using regional and age groupings to assess mercury concentrations in young Alaskan Steller sea lions. The highest concentrations of mercury occurred in the youngest animals, likely via in utero exposure. Based on the adverse developmental outcomes of methylmercury toxicity this specific cohort is of concern. Regionally, higher concentrations of mercury were observed in the endangered western population of Steller sea lions and mirrored patterns observed in human biomonitoring studies of Alaskan coastal communities. These data have broader implications with respect to human and ecosystem health as Steller sea lions rely on similar prey species and foraging areas as those targeted by commercial fisheries and subsistence users and are therefore valuable sentinels of marine ecosystem health.

Mercury Concentrations in Hair from Neonatal and Juvenile Steller Sea Lions (Eumetopias jubatus): Implications Based on Age and Region in this Northern Pacific Marine Sentinel Piscivore

Environmental conditions experienced during early growth and development markedly shape phenotypic traits. Consequently, individuals of the same cohort may show similar life-history tactics throughout life. Conditions experienced later in life, however, could fine-tune these initial differences, either increasing (cumulative effect) or decreasing (compensatory effect) the magnitude of cohort variation with increasing age. Our novel comparative analysis that quantifies cohort variation in individual body size trajectories shows that initial cohort variation dissipates throughout life, and that lifetime patterns change both across species with different paces of life and between sexes. We used longitudinal data on body size (mostly assessed using mass) from 11 populations of large herbivores spread along the “slow-fast” continuum of life histories. We first quantified cohort variation using mixture models to identify clusters of cohorts with similar initial size. We identified clear cohort clusters in all species except the one with the slowest pace of life, revealing that variation in early size is structured among cohorts and highlighting typological differences among cohorts. Growth trajectories differed among cohort clusters, highlighting how early size is a fundamental determinant of lifetime growth patterns. In all species, among-cohort variation in size peaked at the start of life, then quickly decreased with age and stabilized around mid-life. Cohort variation was lower in species with a slower than a faster pace of life, and vanished at prime age in species with the slowest pace of life. After accounting for viability selection, compensatory/catch-up growth in early life explained much of the decrease in cohort variation. Females showed less phenotypic variability and stronger compensatory/catch-up growth than males early in life, whereas males showed more progressive changes throughout life. These results confirm that stronger selective pressures for rapid growth make males more vulnerable to poor environmental conditions early in life and less able to recover after a poor start. Our comparative analysis illustrates how variability in growth changes over time in closely related species that span a wide range on the “slow-fast” continuum, the main axis of variation in life-history strategies of vertebrates.

This article is protected by copyright. All rights reserved.

/pdf/cohort-variation-in-individual-body-mass-dissipates-with-age-2f19l6jsnp.pdf

Cohort variation in individual body mass dissipates with age in large herbivores

Studies of health, survival, and development of juvenile Alaskan Steller sea lions (Eametopias jubatus, SSL) require accurate estimates of age for wild-captured animals. However, the value and accuracy of several potential predictors of age have not been assessed with data from known-age free-ranging animals. During 2001-2005, forty-six individual SSL originally branded or tagged at ≤6 mo of age were recaptured by the Alaska Department of Fish and Game (ADFG followed by DSL, DIAS, and WHIS (r 2 = 0.70, 0.56, and 0.45, respectively). The inclusion of a single sample from a 44-mo-old sea lion suggested quadratic relationships between age and all predictors for older animals. Only models including CTL predicted age to within 6 mo of known age. The equation Age = (-3.0112 + [0.6726 * CTL] + [0.4965 * DIAS]) allows for accurate age estimates of SSL ≤23 mo for both sexes.

A field‐based method for estimating age in free‐ranging steller sea lions (eumetopias jubatus) less than twenty‐four months of age

Steller sea lion (Eumetopias jubatus) pups (n  =  366) were hot-branded at Lowrie Island, Southeast Alaska, USA, in June 2001 and 2002 for vital-rates studies. To assess potential mortality following branding, we estimated weekly survival to 12 weeks postbranding using mark–recapture models. Survival estimates ranged from 0.984/week to 0.988/week, or 0.868 over the 12-week period; varied little with sex, year, and capture area; and were higher for larger than smaller male pups and unexpectedly lower for larger than smaller female pups. Inclusion of resights at 1–3 years of age prevented a −4.5% bias in cumulative survival to 12 weeks postbranding by accounting for pups that survived but permanently emigrated from Lowrie Island during the 12-week survey. Data from double-marked pups (i.e., branded and flipper-tagged) indicated the low brand-misreading probability of 3.1% did not bias survival estimates. Assuming survival differences between the first 2 weeks postbranding and later weeks were due e...

https://www.jstor.org/stable/info/20616760

Postbranding Survival of Steller Sea Lion Pups at Lowrie Island in Southeast Alaska

Information concerning mechanistic processes underlying changes in vital rates and ultimately population growth rate is required to monitor impacts of environmental change on wildlife. We estimated age-specific survival and examined factors influencing survival for a threatened population of Steller sea lions (Eumetopias jubatus) in southeastern Alaska. We used mark-recapture models and data from 1,995 individuals marked at approximately one month of age at four of five rookeries in southeastern Alaska, and resighted from Oregon to the Bering Sea. Average annual survival probability for females was 0.64 for pups and 0.77 for yearlings, and increased from 0.91 to 0.96 from age 3–7 yrs. Annual survival probability of males averaged 0.60 for pups and 0.88 by 7 yrs, resulting in probability of survival to age 7, 33% lower for males compared to females. Pups from northern southeastern Alaska (including an area of low summer population size but rapid growth) were twice as likely to survive to age 7 compared to pups from southern rookeries (including a large, historical, stable rookery). Effects of early conditions on future fitness were observed as (1) environmental conditions in the birth year equally affected first- and second-year survival, and (2) effects of body mass at approximately one month of age were still apparent at 7 yrs. Survival from 0–2 yrs varied among five cohorts by a maximum absolute difference of 0.12. We observed survival costs for long-distance dispersal for males, particularly as juveniles. However, survival was higher for non-pups that dispersed to northern southeastern Alaska, suggesting that moving to an area with greater productivity, greater safety, or lower population size may alleviate a poor start and provide a mechanism for spatial structure for sea lion populations.

https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/ES11-00215.1

Cohort effects and spatial variation in age‐specific survival of Steller sea lions from southeastern Alaska

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A field‐based method for estimating age in free‐ranging steller sea lions (eumetopias jubatus) less than twenty‐four months of age

Postbranding Survival of Steller Sea Lion Pups at Lowrie Island in Southeast Alaska

Cohort effects and spatial variation in age‐specific survival of Steller sea lions from southeastern Alaska