Demographic effects of road mortality on mammalian populations: a systematic review

In light of rapidly expanding road networks worldwide, there is increasing global awareness of the growing amount of mammalian roadkill. However, the ways in which road mortality affects the population dynamics of different species remains largely unclear. We aimed to categorise the demographic parameters in mammalian populations around the world that are directly or indirectly affected by road mortality, as well as identify the most effective study designs for quantifying population-level consequences of road mortality. We conducted a comprehensive systematic review to synthesise literature published between 2000 and 2021 and out of 11,238 unique studies returned, 83 studies were retained comprising 69 mammalian species and 150 populations. A bias towards research-intensive countries and larger mammals was apparent. Although searches were conducted in five languages, all studies meeting the inclusion criteria were in English. Relatively few studies (13.3%) provided relevant demographic context to roadkill figures, hampering understanding of the impacts on population persistence. We categorised five direct demographic parameters affected by road mortality: sex- and age-biased mortality, the percentage of a population killed on roads per year (values up to 50% were reported), the contribution of roadkill to total mortality rates (up to 80%), and roadkill during inter-patch or long-distance movements. Female-biased mortality may be more prevalent than previously recognised and is likely to be critical to population dynamics. Roadkill was the greatest source of mortality for 28% of studied populations and both additive and compensatory mechanisms to roadkill were found to occur, bringing varied challenges to conservation around roads. In addition, intra-specific population differences in demographic effects of road mortality were common. This highlights that the relative importance of road mortality is likely to be context specific as the road configuration and habitat quality surrounding a population can vary. Road ecology studies that collect data on key life parameters, such as age/stage/sex-specific survival and dispersal success, and that use a combination of methods are critical in understanding long-term impacts. Quantifying the demographic impacts of road mortality is an important yet complex consideration for proactive road management.

Raptors, racing pigeons and perceptions of attacks

Raptors are often the cause of human-wildlife conflict because they may predate economically valuable species, and it is the perceived extent of predation that may augment conflict between raptors and people who keep and race pigeons. This study uses data obtained through questionnaires and an online raptor-attack reporting feature to investigate the frequency of racing pigeon losses and the perceptions of pigeon fanciers. Responses suggest that those who kept more pigeons and entered more races lost a higher proportion of pigeons. Losses were also influenced by the predatory species: sparrowhawks (Accipter nisus) were more likely to attack pigeons at lofts, whilst peregrines (Falco peregrinus) were more likely to attack pigeons during training, with patterns linked to the raptors’ breeding seasons. Pigeon fanciers were almost unanimous in their perception that raptors threaten the future of the hobby. Previous studies show that only a small proportion of racing pigeons are likely to be lost to raptors, yet pigeon fanciers believe that raptors are the main cause of losses, highlighting a possible mismatch between the perceived and actual causes of loss. This misconception may be a main source of this human-raptor conflict, so educating pigeon fanciers about the true impact of raptors could help to alleviate the issue. A shift in the beginning of the pigeon racing season by one month, and careful sighting of pigeon lofts in gardens, are also recommended in order to reduce raptor attacks.

Prey availability and intraguild competition regulate the spatiotemporal dynamics of a modified large carnivore guild

Effective conservation management requires an understanding of the spatiotemporal dynamics driving large carnivore density and resource partitioning. In African ecosystems, reduced prey populations and the loss of competing guild members, most notably lion (Panthera leo), are expected to increase the levels of competition between remaining carnivores. Consequently, intraguild relationships can be altered, potentially increasing the risk of further population decline. Kasungu National Park (KNP), Malawi, is an example of a conservation area that has experienced large-scale reductions in both carnivore and prey populations, leaving a resident large carnivore guild consisting of only leopard (Panthera pardus) and spotted hyena (Crocuta crocuta). Here, we quantify the spatiotemporal dynamics of these two species and their degree of association, using a combination of co-detection modeling, time-to-event analyses, and temporal activity patterns from camera trap data. The detection of leopard and spotted hyena was significantly associated with the detection of preferred prey and competing carnivores, increasing the likelihood of species interaction. Temporal analyses revealed sex-specific differences in temporal activity, with female leopard activity patterns significantly different to those of spotted hyena and male conspecifics. Heightened risk of interaction with interspecific competitors and male conspecifics may have resulted in female leopards adopting temporal avoidance strategies to facilitate coexistence. Female leopard behavioral adaptations increased overall activity levels and diurnal activity rates, with potential consequences for overall fitness and exposure to sources of mortality. As both species are currently found at low densities in KNP, increased risk of competitive interactions, which infer a reduction in fitness, could have significant implications for large carnivore demographics. The protection of remaining prey populations is necessary to mitigate interspecific competition and avoid further alterations to the large carnivore guild.

Vehicular tracks and the influence of land use and habitat protection in the British uplands

Uplands cover around 25% of the Earth's land surface and comprise highly sensitive soils and habitats of global ecological importance that together provision a suite of valuable ecosystem services. Access to upland areas for land management and recreation is increasingly dependent on the use of motorised vehicles. However, despite the widely acknowledged detrimental consequences of vehicle track development and use, this activity is not currently quantified or monitored. In this study, surfaced and unsurfaced vehicular tracks, footpaths and land cover in an approximately 5% sample of mainland British uplands (1910 km²) were mapped using aerial imagery dating between 2007 and 2016. An information theory approach was used to identify models that best predicted the presence and extent of surfaced tracks as a function of land cover, protected status, extent of blanket peat, proximity to human population and altitude. A total of 2104 km of track were recorded, with 27% defined as being surfaced. This equates to a mean (±SE) track density of 1.10 ± 0.15 km km^-2 in current use by vehicles across upland Britain. Areas of managed heather and grass-dominated habitat were the primary predictors of the presence and extent of surfaced tracks and we found no evidence that areas of conservation interest with protective designation were less susceptible to track construction. These data indicate that wide-ranging vehicular track networks exist in ecologically sensitive environments across the British uplands, with implications for the integrity of sensitive habitats and soils. Land use and management activities that are not facilitating ecological improvement or conservation appear to be driving the presence of surfaced tracks in 'protected' areas. The findings suggest that: a) urgent review and revision of upland track legislation is required in Great Britain; and b) wider assessment of upland tracks should be undertaken to inform global conservation strategies for these environments.

Beneficial Land Management for Hedgehogs (Erinaceus europaeus) in the United Kingdom

Simple Summary

Hedgehogs are declining in the United Kingdom and are now absent from large areas of agriculture land. This commentary discusses the requirements of hedgehogs and links these to land management options that are currently used to benefit wildlife in agricultural areas. Using our knowledge of hedgehog requirements for population persistence, we suggest which land management practices are likely to be of benefit to hedgehogs in the hope that land owners will adopt some of the suggestions to help maintain and expand existing hedgehog populations across agricultural landscapes of the United Kingdom.

Abstract

Hedgehogs (Erinaceus europaeus) are traditionally thought of as being a rural dwelling species, associated with rural and agricultural landscapes across Europe. However, recent studies have highlighted that hedgehogs are more likely to be found in urban than rural habitats in the United Kingdom. Here, we review the status of rural hedgehog populations across the UK and evaluate the potential benefits of agri-environment schemes for hedgehog persistence, while highlighting a lack of empirical evidence that agri-environment options will benefit hedgehog populations. Our synthesis has implications for future conservation strategies for hedgehogs and insectivorous mammals living in agricultural landscapes, and calls for more empirical studies on agri-environment options and their potential benefits to hedgehogs.

Effects of body size on estimation of mammalian area requirements

Accurately quantifying species' area requirements is a prerequisite for effective area-based conservation. This typically involves collecting tracking data on species of interest and then conducting home-range analyses. Problematically, autocorrelation in tracking data can result in space needs being severely underestimated. Based on the previous work, we hypothesized the magnitude of underestimation varies with body mass, a relationship that could have serious conservation implications. To evaluate this hypothesis for terrestrial mammals, we estimated home-range areas with global positioning system (GPS) locations from 757 individuals across 61 globally distributed mammalian species with body masses ranging from 0.4 to 4000 kg. We then applied block cross-validation to quantify bias in empirical home-range estimates. Area requirements of mammals <10 kg were underestimated by a mean approximately15%, and species weighing approximately100 kg were underestimated by approximately50% on average. Thus, we found area estimation was subject to autocorrelation-induced bias that was worse for large species. Combined with the fact that extinction risk increases as body mass increases, the allometric scaling of bias we observed suggests the most threatened species are also likely to be those with the least accurate home-range estimates. As a correction, we tested whether data thinning or autocorrelation-informed home-range estimation minimized the scaling effect of autocorrelation on area estimates. Data thinning required an approximately93% data loss to achieve statistical independence with 95% confidence and was, therefore, not a viable solution. In contrast, autocorrelation-informed home-range estimation resulted in consistently accurate estimates irrespective of mass. When relating body mass to home range size, we detected that correcting for autocorrelation resulted in a scaling exponent significantly >1, meaning the scaling of the relationship changed substantially at the upper end of the mass spectrum.

Human disturbance has contrasting effects on niche partitioning within carnivore communities

Among species, coexistence is driven partly by the partitioning of available resources. The mechanisms of coexistence and competition among species have been a central topic within community ecology, with particular focus on mammalian carnivore community research. However, despite growing concern regarding the impact of humans on the behaviour of species, very little is known about the effect of humans on species interactions. The aim of this review is to establish a comprehensive framework for the impacts of human disturbance on three dimensions (spatial, temporal and trophic) of niche partitioning within carnivore communities and subsequent effects on both intraguild competition and community structure. We conducted a systematic review of the literature on carnivore niche partitioning (246 studies) and extracted 46 reported effects of human disturbance. We found evidence that human disturbance impacts resource partitioning, either positively or negatively, in all three niche dimensions. The repercussions of such variations are highly heterogeneous and differ according to both the type of human disturbance and how the landscape and/or availability of resources are affected. We propose a theoretical framework of the three main outcomes for the impacts of human disturbance on intraguild competition and carnivore community structure: (i) human disturbance impedes niche partitioning, increasing intraguild competition and reducing the richness and diversity of the community; (ii) human disturbance unbalances niche partitioning and intraguild competition, affecting community stability; and (iii) human disturbance facilitates niche partitioning, decreasing intraguild competition and enriching the community. We call for better integration of the impact of humans on carnivore communities in future research on interspecific competition.

A citizen science based survey method for estimating the density of urban carnivores

Globally there are many examples of synanthropic carnivores exploiting growth in urbanisation. As carnivores can come into conflict with humans and are potential vectors of zoonotic disease, assessing densities in suburban areas and identifying factors that influence them are necessary to aid management and mitigation. However, fragmented, privately owned land restricts the use of conventional carnivore surveying techniques in these areas, requiring development of novel methods. We present a method that combines questionnaire distribution to residents with field surveys and GIS, to determine relative density of two urban carnivores in England, Great Britain. We determined the density of: red fox (Vulpes vulpes) social groups in 14, approximately 1km² suburban areas in 8 different towns and cities; and Eurasian badger (Meles meles) social groups in three suburban areas of one city. Average relative fox group density (FGD) was 3.72 km^-2, which was double the estimates for cities with resident foxes in the 1980’s. Density was comparable to an alternative estimate derived from trapping and GPS-tracking, indicating the validity of the method. However, FGD did not correlate with a national dataset based on fox sightings, indicating unreliability of the national data to determine actual densities or to extrapolate a national population estimate. Using species-specific clustering units that reflect social organisation, the method was additionally applied to suburban badgers to derive relative badger group density (BGD) for one city (Brighton, 2.41 km^-2). We demonstrate that citizen science approaches can effectively obtain data to assess suburban carnivore density, however publicly derived national data sets need to be locally validated before extrapolations can be undertaken. The method we present for assessing densities of foxes and badgers in British towns and cities is also adaptable to other urban carnivores elsewhere. However this transferability is contingent on species traits meeting particular criteria, and on resident responsiveness.

Do power lines and protected areas present a catch-22 situation for Cape vultures (Gyps coprotheres)?

Cape vulture Gyps coprotheres populations have declined across their range due to multiple anthropogenic threats. Their susceptibility to fatal collisions with the expanding power line network and the prevalence of carcasses contaminated with illegal poisons and other threats outside protected areas are thought to be the primary drivers of declines in southern Africa. We used GPS-GSM units to track the movements and delineate the home ranges of five adult (mean ±SD minimum convex polygon area = 121,655±90,845 km(2)) and four immature (mean ±SD minimum convex polygon area = 492,300±259,427 km(2)) Cape vultures to investigate the influence of power lines and their use of protected areas. The vultures travelled more than 1,000 km from the capture site and collectively entered five different countries in southern Africa. Their movement patterns and core foraging ranges were closely associated with the spatial distribution of transmission power lines and we present evidence that the construction of power lines has allowed the species to extend its range to areas previously devoid of suitable perches. The distribution of locations of known Cape vulture mortalities caused by interactions with power lines corresponded to the core ranges of the tracked vultures. Although some of the vultures regularly roosted at breeding colonies located inside protected areas the majority of foraging activity took place on unprotected farmland. Their ability to travel vast distances very quickly and the high proportion of time they spend in the vicinity of power lines and outside protected areas make Cape vultures especially vulnerable to negative interactions with the expanding power line network and the full range of threats across the region. Co-ordinated cross-border conservation strategies beyond the protected area network will therefore be necessary to ensure the future survival of threatened vultures in Africa.

Identifying indicators of illegal behaviour: carnivore killing in human-managed landscapes

Managing natural resources often depends on influencing people's behaviour, however effectively targeting interventions to discourage environmentally harmful behaviours is challenging because those involved may be unwilling to identify themselves. Non-sensitive indicators of sensitive behaviours are therefore needed. Previous studies have investigated people's attitudes, assuming attitudes reflect behaviour. There has also been interest in using people's estimates of the proportion of their peers involved in sensitive behaviours to identify those involved, since people tend to assume that others behave like themselves. However, there has been little attempt to test the potential of such indicators. We use the randomized response technique (RRT), designed for investigating sensitive behaviours, to estimate the proportion of farmers in north-eastern South Africa killing carnivores, and use a modified logistic regression model to explore relationships between our best estimates of true behaviour (from RRT) and our proposed non-sensitive indicators (including farmers' attitudes, and estimates of peer-behaviour). Farmers' attitudes towards carnivores, question sensitivity and estimates of peers' behaviour, predict the likelihood of farmers killing carnivores. Attitude and estimates of peer-behaviour are useful indicators of involvement in illicit behaviours and may be used to identify groups of people to engage in interventions aimed at changing behaviour.

Untangling the roles of fire, grazing and rainfall on small mammal communities in grassland ecosystems

In grassland systems across the globe, ecologists have been attempting to understand the complex role of fire, grazing and rainfall in creating habitat heterogeneity and the consequences of anthropogenic control of these factors on ecosystem integrity and functioning. Using a South African grassland ecosystem as a model, we investigated the impact of fire and grazing pressure on small mammal communities during three differing periods of a rainfall cycle. Over 2 years, 15,203 trap nights revealed 1598 captures of 11 species (nine rodents, one macroscelid and one insectivore). Results highlighted the importance of the interplay between factors and showed that the role of fire, grazing and rainfall in determining small mammal abundance was species-dependant. While no two species were affected by the same environmental variables, grass cover or height was important to 56% of species. Considered independently, high rainfall had a positive influence on small mammal abundance and diversity, although the lag period in population response was species-specific. High grazing negatively affected overall abundance, but specifically in Mastomys coucha; fire alone had little immediate impact on small mammal diversity. Six months after the fire, vegetation cover had recovered to similar levels as unburned areas, although small mammal diversity and richness were higher in burned areas than unburned areas. Grazing levels influenced the rate of vegetation recovery. In conclusion, low-level grazing and burning can help to maintain small mammal biodiversity, if conducted under appropriate rainfall levels. A too high grazing pressure, combined with fire, and/or fire conducted under drought conditions can have a negative impact on small mammal biodiversity. To maintain small mammal diversity in grassland ecosystems, the combined effects of the previous year's rainfall and existing population level as well as the inhibition of vegetation recovery via grazing pressure need to be taken into consideration before fire management is applied.

The anesthetic management of triplet cesarean delivery: a retrospective case series of maternal outcomes

Spinal anesthesia for the cesarean delivery of triplets is associated with an increased incidence of maternal hypotension and placental hypoperfusion. We performed a retrospective case series analysis between January 1992 and June 2000 to evaluate the effects of regional anesthetic techniques for cesarean delivery in triplet pregnancies on maternal and neonatal outcome. Spinal and epidural anesthesia were compared with respect to intraoperative hemodynamics and neonatal outcomes. Ninety-six triplet pregnancies were delivered by cesarean section, of which 91 received regional anesthesia. A statistically significant decrease in systolic blood pressure was demonstrated immediately after the induction of spinal as compared with epidural anesthesia. The total volume of IV crystalloid used was significantly larger in the Spinal Anesthesia group. The number of patients receiving more than 15 mg of ephedrine and the cumulative dose of ephedrine was significantly larger in the Spinal group compared with the Epidural group. There were no differences in the rate of perioperative complications between the Spinal and Epidural Anesthesia groups. Neonatal Apgar scores were similar in both groups. The data suggest that both epidural and spinal anesthesia for triplet cesarean delivery are safe techniques, but the latter is associated with a larger initial decrease in systolic blood pressure. This decreasing of systolic blood pressure, however, remained within the physiological range and did not seem to be clinically significant. The need for more crystalloid fluids and ephedrine should be anticipated when spinal anesthesia is used for these cases.

IMPLICATIONS

A large retrospective case series of the effects of spinal and epidural anesthesia on maternal hemodynamic profile during cesarean delivery for triplet gestation was performed. Our findings suggest that spinal anesthesia results in outcomes comparable to epidural anesthesia for both mother and newborns.

The obstetrical anaesthesia assessment clinic: a review of six years experience

We reviewed the out-patient consultation notes of 136 pregnant women seen at the Ottawa Civic Hospital from 1985 to 1991 to evaluate the efficacy of an Obstetric Anaesthesia Assessment Clinic (OAC). In addition, their anaesthetic records from labour and delivery were reviewed. For each patient the reason for referral was recorded according to the involved organ system. The anaesthetic management at delivery was compared with the proposed anaesthetic plan by the OAC consultant (obstetric anaesthetist). The majority of women 84 (62%) had complaints related to the musculo-skeletal system. In addition, 18 patients were referred because of previous anaesthetic problems, ten with a history of cardiac disease, and eight with neurological disease. Lumbar epidural analgesia (LEA) was a safe and effective choice for parturients with low back pain, history of lumbar fractures or single level discectomies without lumbar fusion. Parturients with posterior instrumentation experienced an increased incidence of inadequate pain relief from LEA. Individualized anaesthetic management plans were executed for parturients with spina bifida occulta, neurological, cardiac, and haematological disease as well as for women, with a history of adverse drug reactions and previous problems with regional or general anaesthesia. It is concluded that the OAC has provided a valuable service to obstetricians and anaesthetists for the anaesthetic management of pregnant women with co-existing disease. The OAC gave an opportunity for patient education regarding anaesthetic options for labour and delivery. The attending anaesthetist was provided with a risk assessment and anaesthetic management plan which was adhered to with only two exceptions. Finally, the obstetrician was given consistent advice regarding anaesthesia management that may affect obstetrical decisions.

Patient-controlled analgesia with epidural meperidine after elective cesarean section

BACKGROUND AND OBJECTIVES

We report the first controlled analysis of the use of patient-controlled epidural meperidine. This randomized, prospective study compares the efficacy and safety of patient-controlled epidural meperidine to conventional intramuscular meperidine for the management of postoperative pain after elective cesarean delivery.

METHODS

After delivery, 60 patients were randomly assigned to receive either conventional intramuscular meperidine therapy or epidural meperidine by a patient-controlled analgesia pump, which was programmed to deliver bolus doses in addition to a continuous background infusion.

RESULTS

Patients in the patient-controlled epidural analgesia group used significantly less meperidine in the first 24 hours after surgery (p < 0.05) and had significantly lower visual analog pain scores (p < 0.05) from three hours postoperatively until study completion at 24 hours. Patients in the patient-controlled epidural analgesia group ambulated sooner (19 +/- 7.8 versus 29.2 +/- 2.2 hours, p < 0.005) and cared for their infants earlier (4.6 +/- 0.9 versus 8.1 +/- 6.8 hours, p < 0.05) than patients receiving intramuscular meperidine. One patient developed a respiratory rate of four breaths per minute, 25 minutes after receiving 75 mg epidural meperidine in the operating room. This was treated with intravenous naloxone. No other serious side effects occurred in either group. Both groups were similar with regard to minor intraoperative and postoperative side effects.

CONCLUSIONS

Patient-controlled epidural meperidine after cesarean delivery more effectively manages postoperative pain than conventional intramuscular use. The technique is preferred by both patients and nursing staff and can be used in the ward setting with appropriate organization and education. Respiratory depression, if it occurs, should present early after epidural bolus administration.

Early respiratory depression during caesarean section following epidural meperidine

A case of respiratory depression which occurred following administration of epidural meperidine during Caesarean section is described. Epidural meperidine, 75 mg (10 mg.ml-1) was given after delivery of the infant to provide postoperative analgesia. Oxygen desaturation (SaO2 90%) and a decrease in respiratory rate (4.min-1) were noted 30 min after epidural meperidine was administered. Naloxone, 0.1 mg, was given iv which resulted in prompt improvement in both respiratory rate and oxygen saturation. Vascular absorption of meperidine from the epidural venous plexus is the most probable explanation for this case of early respiratory depression. We recommend a maximum bolus dose of 50 mg of epidural meperidine for pain management after Caesarean section. It is also important to monitor oxygen saturation continuously during the intraoperative period, and to monitor the patient closely in the recovery room for at least one hour for evidence of respiratory depression.

Sacralization of epidural block with repeated doses of 0.25% bupivacaine during labor

A descriptive analysis of the progression of epidural block with repeated doses of 0.25% bupivacaine was performed, assessing pain relief (visual analog scoring), dermatomal spread of sensory and motor block, and the associated management and outcome of labor. The influence of epinephrine 1:200,000 on these observations was also assessed by the random assignment of study patients into two groups, one receiving 10 ml of 0.25% bupivacaine plain (n = 28) and another group receiving 10 ml of 0.25% bupivacaine with commercially added epinephrine 1:200,000 (n = 27). Only primigravid patients were studied. Data comparisons were considered significant at p less than 0.05. With repeated doses of 0.25% bupivacaine, administered within fixed dosing intervals of 60-90 minutes, there was an increasing spread of sensory block toward sacral dermatomes while the upper level of sensory block did not change. Sacral sensory analgesia was present in only 3.5% of patients after the first dose of bupivacaine but was evident in 63.2% of patients following the fourth epidural injection. A similar increase in the number of patients with significant motor weakness was also seen as the number of top-up doses increased. A comparison of patients receiving plain solutions and epinephrine containing bupivacaine showed similar demographic profiles between the groups. Both groups received a similar dose of bupivacaine and experienced comparable management and outcome of labor. Epinephrine in a 1:200,000 concentration did not influence the changing characteristics of the epidural block over time. The duration of labor was not significantly different between groups (10.3 +/- 5.2 hours for the plain group and 11.0 +/- 4.7 hours for the epinephrine group).(ABSTRACT TRUNCATED AT 250 WORDS)