Sexual selection is frequently invoked to explain sexual dimorphism in characters such as the head size of lizards. For many species previously studied, it has been shown that male heads are larger ...than females heads at a given body size. This increased relative head size in males at sexual maturity is associated with advantages of large heads in intrasexual encounters. Males of the iguanid lizard Sceloporus undulatus have larger heads than females of similar size, but the difference is largely accounted for by a reduction in the rate of head growth relative to body-size growth in females rather than strictly by a relative increase in male head size. Presumably, females invest mostly in body growth and reproduction at the expense of an increase in head size once sexual maturity is reached. Consequently, we caution future investigators against attributing sexual differences in morphological characters to sexual selection unless independent data (e.g., behaviors) implicate morphological characters as determinants of differential reproductive success.
The ability of male and female Eublepharis macularius to discriminate among pheromones of males and females and a blank control was investigated. Stimuli were presented on ceramic tiles in the ...animal's home cages. Males tongue-flicked at significantly lower rates in response to male stimuli than to female and control stimuli. Males also performed aggressive behaviors toward male, but not female or control, stimuli, and tail vibrations toward female, but not male or control, stimuli. Mean tongue-flick rates by females did not differ significantly among conditions. Discrimination of male pheromones by females was demonstrated by greater performance of labial-licking and chin-rubbing in response to male stimuli than to either female or control stimuli.PUBLICATION ABSTRACT
Abstract
Background
Pulmonary artery systolic pressure (PASP) is increasingly used as an important datapoint in clinical decision-making and prognostication even in specialties outside of cardiology. ...Estimation of PASP by Doppler quantification using tricuspid regurgitation (TR) peak velocity is commonly used and correlates well with invasive measurement by right heart catheterization. Further study of transthoracic echocardiogram (TTE) techniques to estimate PASP is needed to provide this datapoint in the absence of sufficient Doppler data for the TR peak velocity method. One technique using right ventricular outflow tract acceleration time (AT) to estimate mean pulmonary artery pressure (MPAP) has been proposed by Dabestani Et al. by the equation MPAP=90-(0.62x AT). Assuming a linear relationship between MPAP and PASP, as suggested by Chemla Et al. by MPAP=(0.61xPASP)+2, a modified formula PASP=145-AT could possibly estimate a normal PASP ≤25 mmHg.
Purpose
To examine if a modified Dabestani-Mahan formula PASP=145-AT can estimate a normal PASP ≤25 mmHg as calculated by the TR peak velocity method.
Methods
We queried the electronic medical record at our institution for a sample of 300 patients who had a TTE performed between 2017 and 2020. Each TTE was reviewed and PASP was estimated for each using the TR peak velocity method. A right atrial pressure of 3 mmHg, 8 mmHg, or 15 mmHg was used in the estimation based on inferior vena cava diameter and collapsibility in keeping with the 2015 American Society of Echocardiography guidelines. A short axis view of pulmonary flow using the pulse-waved Doppler sample volume over the transpulmonary valve jet was then reviewed. The time from onset of ejection to peak flow velocity was measured manually as AT in milliseconds using Change Healthcare Cardiology Web Software Package 14.1.1. The measured AT was averaged over three cardiac cycles. Patients with a heart rate between 60 and 100 beats per minute at time of TTE and with sufficient Doppler data to estimate PASP by TR peak velocity and to measure AT were included in a logistic regression analysis.
Results
154 patients were included in the statistical analysis. Patients who had a right ventricular outflow tract acceleration time greater than 120 milliseconds, giving a PASP ≤25 mmHg by the modified formula PASP=145-AT, had a 36 times greater odds of having a PASP ≤25 mmHg by the TR peak velocity method (OR=36.0, 95% CI=10.36–125.12, p<0.001).
Conclusion(s)
Based on a single-center sample, a right ventricular outflow tract acceleration time greater than 120 milliseconds could be used to estimate a normal pulmonary artery systolic pressure less than or equal to 25 mmHg in the absence of sufficient Doppler data for the commonly used TR peak velocity method.
Funding Acknowledgement
Type of funding sources: None.
Male fitness in many species depends strongly on social behaviors needed to obtain fertilizations and prevent loss of fertilizations to other males, but courtship, copulation, and fighting may incur ...increased risk of predation. When demands for reproductive and antipredatory behaviors conflict, fitness may be maximized by accepting some degree of risk to enhance reproductive success. To examine such tradeoffs, I introduced tethered conspecific males or females to adult male broad-headed skinks, Eumeces laticeps, in the field and observed how close they allowed a simulated predator (me) to approach before fleeing, or their latency to approach an introduced female located at different distances from the predator. When conspecific males were introduced, isolated and mate-guarding males initiated agonistic behaviors and permitted closer approach than control males, and mate-guarding males permitted closer approach than isolated males. When females were introduced, both isolated and mate-guarding males courted the introduced females and isolated males permitted closer approach than did mate-guarding males. These results for introduced males and females suggest that increasing risk was accepted when reproductive benefits were greater. Latency for isolated males to approach a conspecific female was greater when the predator was closer to the female, further suggesting sensitivity to predation risk during a reproductive opportunity. Relationships between reproductive and antipredatory behaviors have been studied much less than those between feeding and antipredatory behaviors, but this study indicates that animals balance increased risk of predation with the opportunity to perform several reproductively important behaviors.
Varanid lizards often tongue-flick in feeding and social contexts, but little is known regarding their abilities to identify a variety of prey using only chemical cues or to detect pheromones. We ...studied responses by juvenile Varanus exanthematicus to surface chemical stimuli from several animal taxa, two plant species palatable to herbivorous lizards, and conspecifics, using diluted cologne and deionized water as pungency and odorless controls. In 60-sec trials with stimuli presented on cotton swabs, lizards showed stronger responses to prey stimuli from mouse, cricket, earthworm, and a gekkonid lizard than to control stimuli. These findings suggest that the lizards are able to locate and identify prey from a wide variety of taxa, which would be adaptive for a generalist predator. Only mouse and cricket stimuli induced a greater proportion of individuals to bite swabs than control stimuli. Because these prey were the laboratory diet, biting frequency may depend on familiarity with the prey. Like other tested insectivores and carnivores, V. exanthematicus showed no signs of discriminative responses to plant chemicals. The lizards tongue-flicked in response to conspecific cues at a higher rate than to the odorless control but at a lower rate than to cues from a gekkonid lizard, indicating that conspecific cues were detected and discriminated from prey cues.
Cologne has been used extensively as a pungency control in experiments on chemosensory behavior to assess responses to an odorous, readily detectable stimulus that is irrelevant to the adaptive ...response being studied. However, undiluted cologne may be aversive, its effects might differ among brands, it might suppress responses to simultaneously presented chemical stimuli, and might affect subsequent responsiveness to other stimuli. We present experimental data showing that undiluted cologne can be aversive, but that aversion can be eliminated by dilution. We also show that the utility of cologne as a pungency control varies among brands, that cologne does not suppress responses to food chemicals in some species, but does in others, and that prior exposure to cologne does not affect later response to food chemicals. In 60 s swab trials with the Balearic lizard (Podarcis lilfordi), the main chemosensory responses were unaffected by cologne concentration. However, one-fourth of lizards exhibited slight to moderate aversion to undiluted cologne and 3:1 water:cologne, but not to a readily detected lower concentration (9:1). Two cologne brands did not affect responses, but a third brand induced increased tongue-flick rates. Colognes that stimulate increased tongue-flicking might mask real experimental effects. Cologne presented simultaneously with cricket chemicals did not affect tongue-flicking and biting responses in two species, but caused increased tongue-flicking in a third species and weaker response to cricket chemicals in a fourth. Prior testing with cologne did not affect responsiveness to cricket chemicals in a subsequent trial. Although cologne is a useful pungency control, pilot tests are needed to verify its utility for unstudied cologne types and animal species.
Prey must balance gains from activities such as foraging and social behavior with predation risk. Optimal escape theory has been successful in predicting escape behavior of prey under a range of risk ...and cost factors. The optimal approach distance, the distance from the predator at which prey should begin to flee, occurs when risk equals cost. Optimal escape theory predicts that for a fixed cost, the approach distance increases as risk increases. It makes no predictions about approach distance for prey in refuges that provide only partial protection or about escape variables other than approach distance, such as the likelihood of stopping before entering refuge and escape speed. By experimentally simulating a predator approaching keeled earless lizards, Holbrookia propinqua, the predictions of optimal escape theory for two risk factors, predator approach speed and directness of approach were tested. In addition, predictions that the likelihood of fleeing into refuge without stopping and the speed of escape runs increase with risk, in this case predator approach speed, and that lizards in incompletely protective refuges permit closer approach than lizards not in refuges were also tested. Approach distance increased with predator approach speed and directness of approach, confirming predictions of optimal escape theory. Lizards were more likely to enter refuge and ran faster when approached rapidly, verifying that predation risk affects escape decisions by the lizards for escape variables not included in optimal escape theory. They allowed closer approach when in incompletely protective refuges than when in the open, confirming the prediction that risk affects escape decisions while in refuge. Optimal escape theory has been highly successful, but testing it has led to relative neglect of important aspects of escape other than approach distance.
During encounters with predators, prey must balance the degree of risk against the loss of fitness-enhancing benefits such as feeding and social activities. Most studies of tradeoffs between risk and ...cost of escaping have measured flight initiation distance and time to emerge from refuge, for which theory provides robustly supported predictions. Tradeoffs involving other aspects of encounters, including distance fled and time between escape and return to a food source, have received little theoretical or empirical attention. By adapting models of flight initiation distance and time between entry into refuge and emergence, we predict effects of predation risk and cost on distance fled and time to return to a source of benefit after fleeing. Acting as simulated predators that approached at a fixed speed, we conducted an experimental field study to test the hypotheses that flight initiation distance, distance fled, and time to return to food by Balearic lizards (Podarcis lilfordi) decrease with the presence and amount of insect food. Predictions of the models were strongly supported, including those for distance fled and return time, but predictions for other cost factors and predation risk factors remain to be tested.
Because predators attacking from above may cast shadows on prey, diverse prey have evolved behavioural responses (fleeing, freezing, descending in water) to shadowing. I studied escape responses to ...shadow in three lizard species by passing my hand overhead, casting a shadow on them or not. Theory predicts immediate fleeing when a predator is detected closer than the optimal flight initiation distance (predator-prey distance when escape begins). Predictions that Sceloporus virgatus, S. jarrovii and Urosaurus ornatus are more likely to flee and to either flee or adopt alert postures when covered by shadow were verified. Probability of fleeing or alerting did not differ among age/sex groups in S. virgatus. For probability of fleeing, shadow and age/sex group effects interacted, juveniles seeming to be slightly less likely to flee from shadow. Sceloporus virgatus covered by shadow fled more frequently on horizontal than vertical surfaces, when fully exposed than beneath overhanging objects, and when shadow encroached rapidly than slowly. These findings are consistent with the hypothesis that probability of fleeing is greater when shadow is more likely to indicate attack. Responses to sudden covering by shadow conform to predictions based of escape theory based on predation risk.
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