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Geology topics

K.A. Bjorndal

Publications and source records attributed to K.A. Bjorndal.

6 recordsLinked to original sources
USGS2020

Turtles and tortoises are in trouble

Turtles and tortoises (chelonians) have been integral components of global ecosystems for about 220 million years and have played important roles in human culture for at least 400,000 years. The chelonian shell is a remarkable evolutionary adaptation, facilitating success in terrestrial, freshwater and marine ecosystems. Today, more than half of the 360 living species and 482 total taxa (species and subspecies combined) are threatened with extinction. This places chelonians among the groups with the highest extinction risk of any sizeable vertebrate group. Turtle populations are declining rapidly due to habitat loss, consumption by humans for food and traditional medicines and collection for the international pet trade. Many taxa could become extinct in this century. Here, we examine survival threats to turtles and tortoises and discuss the interventions that will be needed to prevent widespread extinction in this group in coming decades.

Current Biology↗
USGS2016

Are we working towards global research priorities for management and conservation of sea turtles?

In 2010, an international group of 35 sea turtle researchers refined an initial list of more than 200 research questions into 20 metaquestions that were considered key for management and conservation of sea turtles. These were classified under 5 categories: reproductive biology, biogeography, population ecology, threats and conservation strategies. To obtain a picture of how research is being focused towards these key questions, we undertook a systematic review of the peer-reviewed literature (2014 and 2015) attributing papers to the original 20 questions. In total, we reviewed 605 articles in full and from these 355 (59%) were judged to substantively address the 20 key questions, with others focusing on basic science and monitoring. Progress to answering the 20 questions was not uniform, and there were biases regarding focal turtle species, geographic scope and publication outlet. Whilst it offers some meaningful indications as to effort, quantifying peer-reviewed literature output is obviously not the only, and possibly not the best, metric for understanding progress towards informing key conservation and management goals. Along with the literature review, an international group based on the original project consortium was assigned to critically summarise recent progress towards answering each of the 20 questions. We found that significant research is being expended towards global priorities for management and conservation of sea turtles. Although highly variable, there has been significant progress in all the key questions identified in 2010. Undertaking this critical review has highlighted that it may be timely to undertake one or more new prioritizing exercises. For this to have maximal benefit we make a range of recommendations for its execution. These include a far greater engagement with social sciences, widening the pool of contributors and focussing the questions, perhaps disaggregating ecology and conservation.

Endangered Species Research↗
USGS2010

Global research priorities for sea turtles: Informing management and conservation in the 21st century

Over the past 3 decades, the status of sea turtles and the need for their protection to aid population recovery have increasingly captured the interest of government agencies, non-governmental organisations (NGOs) and the general public worldwide. This interest has been matched by increased research attention, focusing on a wide variety of topics relating to sea turtle biology and ecology, together with the interrelations of sea turtles with the physical and natural environments. Although sea turtles have been better studied than most other marine fauna, management actions and their evaluation are often hindered by the lack of data on turtle biology, human–turtle interactions, turtle population status and threats. In an effort to inform effective sea turtle conservation a list of priority research questions was assembled based on the opinions of 35 sea turtle researchers from 13 nations working in fields related to turtle biology and/or conservation. The combined experience of the contributing researchers spanned the globe as well as many relevant disciplines involved in conservation research. An initial list of more than 200 questions gathered from respondents was condensed into 20 metaquestions and classified under 5 categories: reproductive biology, biogeography, population ecology, threats and conservation strategies.

Endangered Species Research↗
USGS2001

Historical overfishing and the recent collapse of coastal ecosystems

A method for calculating parameters necessary to maintain stable populations is described and the management implications of the method are discussed. This method depends upon knowledge of the population mortality rate schedule, the age at which the species reaches maturity, and recruitment rates or age ratios in the population. Four approaches are presented which yield information about the status of the population: (1) necessary production for a stable population, (2) allowable mortality for a stable population, (3) annual rate of change in population size, and (4) age ratios in the population which yield a stable condition. General formulas for these relationships, and formulas for several special cases, are presented. Tables are also presented showing production required to maintain a stable population with the simpler (more common) mortality and fecundity schedules.

Science↗
USGS1995

Identification of sex in hatchling loggerhead turtles (Caretta caretta) by analysis of steroid concentrations in chorioallantoic/amniotic fluid

A major difficulty in sea turtle conservation is the inability to nonlethally and noninvasively identify the sex of hatchling sea turtles. Traditional sexing techniques such as plasma sex steroid quantification cannot be applied to hatchlings without sacrificing the hatchlings or utilizing invasive procedures. This paper presents a technique for sexing hatchling sea turtles by analysis of sex steroid concentrations in egg chorioallantoic/amniotic fluid (CAF). Metabolites of estradiol-17β (E) and testosterone (T) in CAF are best expressed as an index or E:T ratio. Chorioallantoic/amniotic fluid E:T ratios for males (0.5 ± 0.1) were significantly lower than those for females (2.2 ± 0.3). When separated by utilizing an E:T ratio of 1.25 as the determinant index value, 27 of 28 hatchlings were designated correctly as males (E:T < 1.25) or females (E:T ⩾ 1.25). Sex was verified for all hatchlings by gonadal histology. This study shows significant concentrations of T and E metabolites in CAF and plasma of hatchling loggerhead turtles and illustrates the use of a nonlethal, noninvasive method for determining sex, which could be potentially utilized for other endangered reptile and avian species.

Florida, North Carolina↗