Terrestrial mesopredators did not increase after top-predator removal in a large-scale experimental test of mesopredator release theory.

Removal or loss of top-predators has been predicted to cause cascading negative effects for ecosystems, including mesopredator release. However, reliable evidence for these processes in terrestrial systems has been mixed and equivocal due, in large part, to the systemic and continued use of low-inference study designs to investigate this issue. Even previous large-scale manipulative experiments of strong inferential value have been limited by experimental design features (i.e. failure to prevent migration between treatments) that constrain possible inferences about the presence or absence of mesopredator release effects. Here, we build on these previous strong-inference experiments and report the outcomes of additional large-scale manipulative experiments to eradicate Australian dingoes from two fenced areas where dingo migration was restricted and where theory would predict an increase in extant European red foxes, feral cats and goannas. We demonstrate the removal and suppression of dingoes to undetectable levels over 4-5 years with no corresponding increases in mesopredator relative abundances, which remained low and stable throughout the experiment at both sites. We further demonstrate widespread absence of negative relationships between predators, indicating that the mechanism underpinning predicted mesopredator releases was not present. Our results are consistent with all previous large-scale manipulative experiments and long-term mensurative studies which collectively demonstrate that (1) dingoes do not suppress red foxes, feral cats or goannas at the population level, (2) repeated, temporary suppression of dingoes in open systems does not create mesopredator release effects, and (3) removal and sustained suppression of dingoes to undetectable levels in closed systems does not create mesopredator release effects either. Our experiments add to similar reports from North America, Asia, Europe and southern Africa which indicate that not only is there a widespread absence of reliable evidence for these processes, but there is also a large and continually growing body of experimental evidence of absence for these processes in many terrestrial systems. We conclude that although sympatric predators may interact negatively with each other on smaller spatiotemporal scales, that these negative interactions do not always scale-up to the population level, nor are they always strong enough to create mesopredator suppression or release effects.

Relationship Between Maternal Serum Bile Acid Levels and Fetal Cardiac Troponin-I Levels in Asymptomatic Pregnant Patients at Term: A Cross-sectional Observational Study.

Objective The objective of our study was to determine if a correlation exists between maternal total bile acid levels, degree of maternal pruritus, and fetal cardiac troponin-I levels in asymptomatic patients without a diagnosis of intrahepatic cholestasis of pregnancy. Study design In this cross-sectional observational study, patients were enrolled at the time of the scheduled term cesarean section. Maternal blood was drawn for fasting total bile acid levels and cord blood was collected for fetal cardiac troponin-I levels. Pruritus during pregnancy was quantified by the patient on a visual analog scale (VAS). Correlation coefficients between these variables were calculated. Results There was not a positive correlation between any of the primary variables studied (pruritis, total bile acid, cardiac troponin I). Pearson's R between total bile acid and cardiac troponin I was -0.058 (weak correlation in the opposite direction), and between total bile acid and pruritus severity, it was 0.031. Conclusion In patients without intrahepatic cholestasis of pregnancy, higher levels of maternal total bile acids did not correlate with increased cardiac troponin-I (fetal cardiomyocyte damage) or increased pruritus. This supports the current theory that the adverse outcomes associated with intrahepatic cholestasis of pregnancy require a threshold value of total bile acids, one high enough to cause clinically significant maternal pruritis.

Diet of dingoes and other wild dogs in peri-urban areas of north-eastern Australia.

Knowledge of the resource requirements of urban predators can improve our understanding of their ecology and assist town planners and wildlife management agencies in developing management approaches that alleviate human-wildlife conflicts. Here we examine food and dietary items identified in scats of dingoes in peri-urban areas of north-eastern Australia to better understand their resource requirements and the potential for dingoes to threaten locally fragmented populations of native fauna. Our primary aim was to determine what peri-urban dingoes eat, and whether or not this differs between regions. We identified over 40 different food items in dingo scats, almost all of which were mammals. Individual species commonly observed in dingo scats included agile wallabies, northern brown bandicoots and swamp wallabies. Birds were relatively common in some areas but not others, as were invertebrates. Dingoes were identified as a significant potential threat to fragmented populations of koalas. Dietary overlap was typically very high or near-identical between regions, indicating that peri-urban dingoes ate the same types or sizes of prey in different areas. Future studies should seek to quantify actual and perceived impacts of, and human attitudes towards, peri-urban dingoes, and to develop management strategies with a greater chance of reducing human-wildlife conflicts.

Evaluating and validating abundance monitoring methods in the absence of populations of known size: review and application to a passive tracking index.

Rarely is it possible to obtain absolute numbers in free-ranging populations and although various direct and indirect methods are used to estimate abundance, few are validated against populations of known size. In this paper, we apply grounding, calibration and verification methods, used to validate mathematical models, to methods of estimating relative abundance. To illustrate how this might be done, we consider and evaluate the widely applied passive tracking index (PTI) methodology. Using published data, we examine the rationality of PTI methodology, how conceptually animal activity and abundance are related and how alternative methods are subject to similar biases or produce similar abundance estimates and trends. We then attune the method against populations representing a range of densities likely to be encountered in the field. Finally, we compare PTI trends against a prediction that adjacent populations of the same species will have similar abundance values and trends in activity. We show that while PTI abundance estimates are subject to environmental and behavioural stochasticity peculiar to each species, the PTI method and associated variance estimate showed high probability of detection, high precision of abundance values and, generally, low variability between surveys, and suggest that the PTI method applied using this procedure and for these species provides a sensitive and credible index of abundance. This same or similar validation approach can and should be applied to alternative relative abundance methods in order to demonstrate their credibility and justify their use.

Intraguild relationships between sympatric predators exposed to lethal control: predator manipulation experiments.

INTRODUCTION: Terrestrial top-predators are expected to regulate and stabilise food webs through their consumptive and non-consumptive effects on sympatric mesopredators and prey. The lethal control of top-predators has therefore been predicted to inhibit top-predator function, generate the release of mesopredators and indirectly harm native fauna through trophic cascade effects. Understanding the outcomes of lethal control on interactions within terrestrial predator guilds is important for zoologists, conservation biologists and wildlife managers. However, few studies have the capacity to test these predictions experimentally, and no such studies have previously been conducted on the eclectic suite of native and exotic, mammalian and reptilian taxa we simultaneously assess. We conducted a series of landscape-scale, multi-year, manipulative experiments at nine sites spanning five ecosystem types across the Australian continental rangelands to investigate the responses of mesopredators (red foxes, feral cats and goannas) to contemporary poison-baiting programs intended to control top-predators (dingoes) for livestock protection. RESULT: Short-term behavioural releases of mesopredators were not apparent, and in almost all cases, the three mesopredators we assessed were in similar or greater abundance in unbaited areas relative to baited areas, with mesopredator abundance trends typically either uncorrelated or positively correlated with top-predator abundance trends over time. The exotic mammals and native reptile we assessed responded similarly (poorly) to top-predator population manipulation. This is because poison baits were taken by multiple target and non-target predators and top-predator populations quickly recovered to pre-control levels, thus reducing the overall impact of baiting on top-predators and averting a trophic cascade. CONCLUSIONS: These results are in accord with other predator manipulation experiments conducted worldwide, and suggest that Australian populations of native prey fauna at lower trophic levels are unlikely to be negatively affected by contemporary dingo control practices through the release of mesopredators. We conclude that contemporary lethal control practices used on some top-predator populations do not produce the conditions required to generate positive responses from mesopredators. Functional relationships between sympatric terrestrial predators may not be altered by exposure to spatially and temporally sporadic application of non-selective lethal control.

The underestimation of a glass injury to the hand.

This study sought to ascertain the differences between what is found on an orthopedic preoperative examination of a glass injury to the hand and the actual intraoperative deficiencies noted in the operating room. The cases of 34 patients who presented to our institution for a shattered glass laceration to the hand, forearm, or wrist between 1998 and 2001 were reviewed. The preoperative examination significantly underestimated the amount of damage to tendons, arteries and nerves. The most frequent injury pattern was the flexor digitorum superficialis (34/103 = 33%), the radial artery (7/18 = 39%), and the superficial branch of the radial nerve (7/32 = 22%). A glass injury to the hand can be a deceivingly debilitating and significant injury. The preoperative examination, even when specifically evaluating for deficiencies, significantly underestimates the extent of damage. If glass is implicated as a causative agent, careful orthopedic evaluation and surgical management should be considered even in light of a normal preoperative examination.

Turf toe: ligamentous injury of the first metatarsophalangeal joint.

Injuries to the metatarsophalangeal (MTP) joint of the great toe have increased in incidence over the past thirty years following the introduction of artificial playing surfaces and the accompanying use of lighter footwear. Although most common in American football players, similar injuries can also occur in other sporting activities including soccer and dance, or following trauma to the great toe. The mechanism of injury is typically hyperextension of the MTP joint, but injuries have also been reported secondary to valgus or varus stress, or rarely as a result of hyperflexion injury. The abnormal forces applied to the first MTP joint at the time of injury, result in varying degrees of sprain or disruption of the supporting soft tissue structures, leading to the injury commonly referred to as turf toe. The extent of soft tissue disruption is influential in treatment planning and can be used to determine the prognosis for recovery. This report will review the anatomy of the first MTP join, followed by a discussion of the mechanism of injury and the typical clinical presentation of an individual with turf toe. Finally, the role of imaging including radiography and magnetic resonance imaging, and standard treatment options for turf toe will be discussed.

Molecules, muscles, and machines: universal performance characteristics of motors.

Animal- and human-made motors vary widely in size and shape, are constructed of vastly different materials, use different mechanisms, and produce an enormous range of mass-specific power. Despite these differences, there is remarkable consistency in the maximum net force produced by broad classes of animal- and human-made motors. Motors that use force production to accomplish steady translational motion of a load (myosin, kinesin, dynein, and RNA polymerase molecules, muscle cells, whole muscles, winches, linear actuators, and rockets) have maximal force outputs that scale as the two-thirds power of mass, i.e., with cross-sectional area. Motors that use cyclical motion to generate force and are more subject to multiaxial stress and vibration have maximal force outputs that scale as a single isometric function of motor mass with mass-specific net force output averaging 57 N x kg(-1) (SD = 14). Examples of this class of motors includes flying birds, bats, and insects, swimming fish, various taxa of running animals, piston engines, electric motors, and all types of jets. Dependence of force production and stress resistance on cross-sectional area is well known, but the isometric scaling and common upper limit of mass-specific force production by cyclical motion motors has not been recognized previously and is not explained by an existing body of theory. Remarkably, this finding indicates that most of the motors used by humans and animals for transportation have a common upper limit of mass-specific net force output that is independent of materials and mechanisms.