73 research outputs found
Home range, habitat selection and activity patterns of an arid-zone population of Temminck’s ground pangolins, Smutsia temminckii
All previous behavioural studies of Temminck’s ground pangolins (Smutsia temminckii) have
focused on populations in mesic regions. We examined home range size, activity periods,
habitat selectivity and refuge site selection of 13 individuals over three years in the Kalahari
Desert of South Africa, near the western edge of the species’ range. Kernel home ranges
of adults averaged 6.5 ± 5.9 km², while juveniles had average home ranges of 6.1 ± 4.0 km².
Reliable prediction of 95% of the Kernel home range required 88 ± 67.7 tracking days. No
significant habitat selectivity was observed. Earthen burrows were the most frequently
used refuge type. The time at which activity commenced varied seasonally as well as among
individuals, with an increase in diurnal activity during winter. Young pangolins also displayed
more diurnal activity compared to adults. Individuals spent 5.7 ± 2.0 hours per 24-hour cycle
outside of refuges, with no significant seasonal variation. Juvenile dispersal peaked during
mid-summer, with individuals travelling up to 49 km from their natal areas. We estimate a
breeding density of 0.16 individuals/km2 and a total density of 0.31 individuals/km2 for our
study area. Our data suggest that activity patterns, movements and refuge selection is similar
across the species’ southern African range, but that densities may be higher in the Kalahari
compared to populations in more mesic eastern areas.National Research Foundation (grant 71454)http://africanzoology.journals.ac.za/tm201
A review of the anthropogenic threats faced by Temminck's ground pangolin, Smutsia temminckii, in southern Africa
Throughout its range, Temminck’s ground pangolin, Smutsia temminckii, is becoming
increasingly threatened, predominantly as a result of anthropogenic pressures. This species
is currently listed as Vulnerable in South Africa and Least Concern globally, although many
assessment criteria are data deficient and thus hamper an accurate assessment of its actual
status. Current knowledge of the threats faced by Temminck’s ground pangolin largely stem
from a handful of ecological studies and ad hoc observations. Here we synthesize data on
the known threats faced by this species in southern Africa and highlight a number of
new threats not previously recognized. The main threats faced by this species include
electrocution on electrified fences, the traditional medicine (muthi ) trade, habitat loss, road
mortalities, capture in gin traps, and potentially poisoning. Electrocutions arguably pose the
greatest threat and mortality rates may be as high as one individual per 11 km of electrified
fence per year. However, the magnitude of the threat posed by the muthi trade has not yet
been quantified. Most southern African countries have adequate legislation protecting
this species, although implementation is often lacking and in some instances the imposed
penalties are unlikely to be a deterrent. We propose mitigating actions for many of the
identified threats, although further research into the efficacy of these actions, and the
development of additional mitigating procedures, is required.The Mohamed bin Zayed Species
Conservation Fund (project 0925713), the National
Research Foundation (grant 71454), Tshwane University of Technology and University of Pretoria.http://www.sawma.co.za/am201
Mapping evaporative water loss in desert passerines reveals an expanding threat of lethal dehydration
Extreme high environmental temperatures produce a variety of consequences for wildlife, including mass die-offs. Heat waves are increasing in frequency, intensity, and extent, and are projected to increase further under climate change. However, the spatial and temporal dynamics of die-off risk are poorly understood. Here, we examine the effects of heat waves on evaporative water loss (EWL) and survival in five desert passerine birds across the southwestern United States using a combination of physiological data, mechanistically informed models, and hourly geospatial temperature data. We ask how rates of EWL vary with temperature across species; how frequently, over what areas, and how rapidly lethal dehydration occurs; how EWL and die-off risk vary with body mass; and how die-off risk is affected by climate warming. We find that smaller-bodied passerines are subject to higher rates of mass-specific EWL than larger-bodied counterparts and thus encounter potentially lethal conditions much more frequently, over shorter daily intervals, and over larger geographic areas. Warming by 4 °C greatly expands the extent, frequency, and intensity of dehydration risk, and introduces new threats for larger passerine birds, particularly those with limited geographic ranges. Our models reveal that increasing air temperatures and heat wave occurrence will potentially have important impacts on the water balance, daily activity, and geographic distribution of arid-zone birds. Impacts may be exacerbated by chronic effects and interactions with other environmental changes. This work underscores the importance of acute risks of high temperatures, particularly for small-bodied species, and suggests conservation of thermal refugia and water sources
Avian thermoregulation in the heat : evaporative cooling capacity of arid-zone Caprimulgiformes from two continents
Birds in the order Caprimulgiformes (nightjars and allies) have a
remarkable capacity for thermoregulation over a wide range of
environmental temperatures, exhibiting pronounced heterothermy in
cool conditions and extreme heat tolerance at high environmental
temperatures. We measured thermoregulatory responses to acute
heat stress in three species of Caprimulgiformes that nest in areas of
extreme heat and aridity, the common poorwill (Phalaenoptilus
nuttallii: Caprimulgidae) and lesser nighthawk (Chordeiles
acutipennis: Caprimulgidae) in the Sonoran Desert of Arizona, and
the Australian owlet-nightjar (Aegotheles cristatus: Aegothelidae) in
the mallee woodlands of South Australia. We exposed wild-caught
birds to progressively increasing air temperatures (Ta) and measured
resting metabolic rate (RMR), evaporative water loss (EWL), body
temperature (Tb) and heat tolerance limit (HTL; the maximum Ta
reached). Comparatively low RMR values were observed in all
species (0.35, 0.36 and 0.40 Wfor the poorwill, nighthawk and owletnightjar,
respectively), with Tb approximating Ta at 40°C and mild
hyperthermia occurring as Ta reached the HTL. Nighthawks and
poorwills reached HTLs of 60 and 62°C, respectively, whereas the
owlet-nightjar had a HTL of 52°C. RMR increased gradually above
minima at Ta of 42, 42 and 35°C, and reached 1.7, 1.9 and 2.0 times
minimum resting values at HTLs in the poorwill, nighthawk and owletnightjar,
respectively. EWL increased rapidly and linearly as Ta
exceeded Tb and resulted in maximum rates of evaporative heat
dissipation equivalent to 237–424% of metabolic heat production.
Bouts of gular flutter resulted in large transient increases in evaporative heat loss (50–123%) accompanied by only small
increments in RMR (<5%). The cavity-nesting/roosting owletnightjar
had a lower HTL and less efficient evaporative cooling
compared with the species that nest and/or roost on open desert
surfaces. The high efficiency of gular flutter for evaporative cooling,
combined with mild hyperthermia, provides the physiological basis for
defending Tb well below Ta in extreme heat and is comparable to the
efficient cooling observed in arid-zone columbids in which cutaneous
EWL is the predominant cooling pathway.The National Science Foundation
under IOS-1122228 to B.O.W.http://jeb.biologists.org2018-10-01am2018Zoology and Entomolog
Avian thermoregulation in the heat : phylogenetic variation among avian orders in evaporative cooling capacity and heat tolerance
Little is known about the phylogenetic variation of avian evaporative
cooling efficiency and heat tolerance in hot environments. We
quantified thermoregulatory responses to high air temperature (Ta) in
∼100-g representatives of three orders, namely, the African cuckoo
(Cuculus gularis, Cuculiformes), lilac-breasted roller (Coracias
caudatus, Coraciiformes) and Burchell’s starling (Lamprotornis
australis, Passeriformes). All three species initiated respiratory
mechanisms to increase evaporative heat dissipation when body
temperature (Tb) approached 41.5°C in response to increasing Ta, with
gular flutter observed in cuckoos and panting in rollers and starlings.
Resting metabolic rate and evaporative water loss increased by
quantitatively similar magnitudes in all three species, although
maximum rates of evaporative water loss were proportionately lower
in starlings. Evaporative cooling efficiency [defined as the ratio of
evaporative heat loss (EHL) to metabolic heat production (MHP)]
generally remained below 2.0 in cuckoos and starlings, but reached a
maximum of ∼3.5 in rollers. The high value for rollers reveals a very
efficient evaporative cooling mechanism, and is similar to EHL/MHP
maxima for similarly sized columbids which very effectively dissipate
heat via cutaneous evaporation. This unexpected phylogenetic
variation among the orders tested in the physiological mechanisms
of heat dissipation is an important step toward determining the
evolution of heat tolerance traits in desert birds.This material is based on work supported by the National Science Foundation under
IOS-1122228 to B.O.W.The National Science Foundation under IOS-1122228 to B.O.W.http://jeb.biologists.org2019-03-01am2018Zoology and Entomolog
Avian thermoregulation in the heat : evaporative cooling in five Australian passerines reveals within-order biogeographic variation in heat tolerance
Evaporative heat loss pathways vary among avian orders, but the
extent to which evaporative cooling capacity and heat tolerance vary
within orders remains unclear. We quantified the upper limits to
thermoregulation under extremely hot conditions in five Australian
passerines: yellow-plumed honeyeater (Lichenostomus ornatus;
∼17 g), spiny-cheeked honeyeater (Acanthagenys rufogularis;
∼42 g), chestnut-crowned babbler (Pomatostomus ruficeps; ∼52 g),
grey butcherbird (Cracticus torquatus; ∼86 g) and apostlebird
(Struthidea cinerea; ∼118 g). At air temperatures (Ta) exceeding
body temperature (Tb), all five species showed increases in Tb to
maximum values around 44–45°C, accompanied by rapid increases
in resting metabolic rate above clearly defined upper critical limits of
thermoneutrality and increases in evaporative water loss (EWL) to
levels equivalent to 670–860% of baseline rates at thermoneutral Ta.
Maximum cooling capacity, quantified as the fraction of metabolic
heat production dissipated evaporatively, ranged from 1.20 to 2.17,
consistent with the known range for passerines, and well below
the corresponding ranges for columbids and caprimulgids. Heat
tolerance limit (HTL, the maximum Ta tolerated) scaled positively with
body mass, varying from 46°C in yellow-plumed honeyeaters to 52°C
in a single apostlebird, but was lower than that of three southern
African ploceid passerines investigated previously. We argue this
difference is functionally linked to a smaller scope for increases in
EWL above baseline levels. Our data reiterate the reliance of
passerines in general on respiratory evaporative heat loss via
panting, but also reveal substantial within-order variation in heat
tolerance and evaporative cooling capacity.The National Science Foundation [IOS-
1122228 to B.O.W.].http://jeb.biologists.org2018-07-30am2017Zoology and Entomolog
Non-invasive measurement of metabolic rates in wild, free-living birds using doubly labelled water
Please read abstract in the article.DST-NRF Centre of Excellence at the FitzPatrick Institute for African Ornithology; National Research Foundation of South Africa, Grant/Award Number: 110506; Universities of Cambridge and Zurich; MAVA Foundation, ERC, Grant/Award Number: 294494; University of Pretoria; The Oppenheimer Memorial Trust, Grant/Award Number: OMT 20747/01http://wileyonlinelibrary.com/journal/fechj2020Mammal Research InstituteZoology and Entomolog
Avian thermoregulation in the heat : evaporative cooling capacity in an archetypal desert specialist, Burchell's sandgrouse (Pterocles burchelli)
Sandgrouse (Pterocliformes) are quintessential examples of avian adaptation to desert
environments, but relatively little is known about the limits to their heat tolerance and
evaporative cooling capacity. We predicted that evaporative cooling in Burchell’s
sandgrouse (Pterocles burchelli) is highly efficient and provides the basis for
tolerance of very high air temperature (Ta). We measured body temperature (Tb),
resting metabolic rate (RMR) and evaporative water loss (EWL) at Ta between 25 °C
and ~58 °C in birds exposed to successive increments in Ta. Normothermic Tb
averaged 39.0 °C, lower than typical avian values. At Ta > 34.5 °C, Tb increased
linearly to a maximum of 43.6 °C at Ta = 56 °C. The upper critical limit of
thermoneutrality (Tuc) was Ta = 43.8 °C, closely coinciding with the onset of panting
and gular flutter. Above the Tuc, RMR increased 2.5-fold to 2.89 W at Ta = 56 °C, a
fractional increase far exceeding that of many other species under comparable
conditions. Rates of EWL increased rapidly at Ta > 42.9 °C to 7.84 ± 0.90 g h-1 at Ta =
56 °C, an 11-fold increase above minimal levels. Maximum evaporative cooling
efficiency (ratio of evaporative heat loss to metabolic heat production) was 2.03, but
could be as high as 2.70 if our assumption that the birds were metabolising lipids is
incorrect. Thermoregulation at very high Ta in P. burchelli was characterised by large
increases in RMR and EWL, and is much less efficient than in taxa such as columbids
and caprimulgids.National Science Foundation under IOS-1122228.http://jeb.biologists.org2017-07-31hb2016Zoology and Entomolog
Population-Based Resequencing of Experimentally Evolved Populations Reveals the Genetic Basis of Body Size Variation in Drosophila melanogaster
Body size is a classic quantitative trait with evolutionarily significant variation within many species. Locating the alleles responsible for this variation would help understand the maintenance of variation in body size in particular, as well as quantitative traits in general. However, successful genome-wide association of genotype and phenotype may require very large sample sizes if alleles have low population frequencies or modest effects. As a complementary approach, we propose that population-based resequencing of experimentally evolved populations allows for considerable power to map functional variation. Here, we use this technique to investigate the genetic basis of natural variation in body size in Drosophila melanogaster. Significant differentiation of hundreds of loci in replicate selection populations supports the hypothesis that the genetic basis of body size variation is very polygenic in D. melanogaster. Significantly differentiated variants are limited to single genes at some loci, allowing precise hypotheses to be formed regarding causal polymorphisms, while other significant regions are large and contain many genes. By using significantly associated polymorphisms as a priori candidates in follow-up studies, these data are expected to provide considerable power to determine the genetic basis of natural variation in body size
Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study
Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe
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