Enhancing the Perceived Threat of Vehicle Approach to Deer

ABSTRACT In North America and Europe, deer (Cervidae)—vehicle collisions (DVCs) are common and result not only in injury and death to the animals involved, but also human injury and property damage. Given that most DVCs occur during crepuscular periods, we questioned whether the perceived threat to deer posed by vehicle approach could be enhanced. We hypothesized that a vehicle-based lighting system that better complements peak visual capabilities of deer at night relative to standard tungsten-halogen (TH) lighting alone would elicit a greater flight-initiation distance (FID) by free-ranging white-tailed deer (Odocoileus virginianus). Our lighting system comprised 2 TH lamps and one Xenarc high-intensity discharge (HID) lamp. We defined an a priori logistic model comprising 4 variables potentially explaining deer FID relative to vehicle approach: 1) starting distance of the approach, 2) lighting treatment, 3) season, and 4) deer group size. Deer exposed to the combination of TH lamps and constant illumination of the HID lamp exhibited a mean (SD) FID of 136 (127) m. In contrast, deer exposed to TH lamps only initiated flight on average at 116 (127) m, and those exposed to the combination of TH lamps and the HID lamp pulsed at 2 Hz exhibited a mean FID of 89 (98) m. We contend that the pulsing of the HID lamp while TH lamps were illuminated resulted in consistent loss (over approx. 0.5-sec intervals) of a portion of the image on approach, possibly interfering with sensory information relative to the position of the potential threat. In contrast, the combination of TH lamps and constant illumination of the HID lamp contributed (P = 0.033) to the probability of a FID ≥94 m. We suggest, therefore, that deer FID can be increased by combining currently available TH and HID lamps, or use of HID lamps alone, to enhance detection of an approaching vehicle at night. Also, we encourage research into new lamp designs to better complement deer visual capabilities as well as continued research to quantify deer FID in response to vehicle approach at night and lamp-specific properties that can enhance deer detection of the vehicle.     

European birds adjust their flight initiation distance to road speed limits

Behavioural responses can help species persist in habitats modified by humans. Roads and traffic greatly affect animals'' mortality not only through habitat structure modifications but also through direct mortality owing to collisions. Although species are known to differ in their sensitivity to the risk of collision, whether individuals can change their behaviour in response to this is still unknown. Here, we tested whether common European birds changed their flight initiation distances (FIDs) in response to vehicles according to road speed limit (a known factor affecting killing rates on roads) and vehicle speed. We found that FID increased with speed limit, although vehicle speed had no effect. This suggests that birds adjust their flight distance to speed limit, which may reduce collision risks and decrease mortality maximizing the time allocated to foraging behaviours. Mobility and territory size are likely to affect an individuals'' ability to respond adaptively to local speed limits.     

Effects of Single‐ and Mixed‐Species Group Composition on the Flight Initiation Distances of Plains and Grevy's Zebras

Zebras, as prey species, attend to the behavior of nearby conspecifics and heterospecifics when making decisions to flee from predators. Plains zebras (Equus quagga) and Grevy's zebras (E. grevyi) frequently form mixed‐species groups in zones where their ranges overlap in Kenya. Although anecdotal observations suggest that Plains zebras are more flighty around humans than Grevy's zebras are, this has not been empirically confirmed, and relatively little is known about how they may influence each other's flight behavior. We addressed these questions by examining the flight initiation distances (FIDs) of Plains and Grevy's zebras in single‐species and mixed‐species groups from an approaching human. One target individual per group was approached steadily on foot, with start distance, alert distance, and FID recorded from this target. Using start distance and alert distance separately as covariates, 22 Plains zebras in single‐species groups exhibited a significantly longer mean FID than 15 Grevy's zebras in single‐species groups. The FIDs of 7 Plains zebras and 5 Grevy's zebras tested in mixed‐species groups were virtually equivalent and intermediate to those of Plains and Grevy's zebras in single‐species groups, suggesting a bidirectional moderating influence of heterospecifics on risk assessment. This effect was most pronounced for Plains zebras in mixed‐species groups that exhibited an FID that was significantly shorter than that of Plains zebras in single‐species groups. Our findings underscore the importance of recognizing that related equids may be differently impacted by anthropogenic stress.     

Avian Risk Assessment: Effects of Perching Height and Detectability

We studied two components of predator risk assessment in birds. While many species are limited to seeking safety under cover or under ground, some birds can fly away from their predators and escape to trees. If birds in fact ‘feel’ safer (e.g. perceive less risk) in trees, we would expect them to tolerate closer approach by a potential terrestrial predator. Another component of safety is at which point the animal detects an approaching threat, which we expected to increase with eye size, assuming eye size is a surrogate for visual acuity. We used the distance birds moved away from an approaching human [flight initiation distance (FID)] as a metric to determine whether birds associated a lower risk of predation by being in trees, and we used the distance at which birds first displayed alert behaviors from an approaching human (alert distance) to determine if birds with larger eyes had higher detection distances. Although some species were affected by tree height, we found no clear pattern that birds assessed themselves to be at a lower risk of predation when they were ≥3 m above the ground compared with being <3 m above ground. In the 10 species for which height had any significant effect on FID, birds ≥3 m off the ground had greater FIDs in six species, but the remaining three species had the opposite response. While we found a significant positive relationship between eye size and alert distance in 23 species, the relationship was not present in a phylogenetic analysis using independent contrasts, which suggests that the apparent relationship was influenced strongly by the association between the studied species. Together, these results suggest that birds do not obviously associate being in a tree with safety, and that variations in visual acuity, per se, cannot be used as a general indicator of differences in alert distances, as previously suggested in the literature.     

Distance from Water,Sex and Approach Direction Influence Flight Distances Among Habituated Black Swans

In many animals, response to predators occurs at greater distances the further an individual is from a refuge, but this has rarely been investigated in birds. Here, we test the hypothesis that the further from refuge (i.e. water) a foraging black swan Cygnus atratus is situated, the longer its flight initiation distance (FID) in response to a pedestrian approach on land. As predicted, swans situated farther from water exhibited longer FIDs compared with those closer to the shore. In addition, there was the possibility of an interesting interaction effect (p < 0.061) of sex and direction of approach on FID. Whilst males tended to not alter their response in relation to the angle of approach relative to the water, females tended to respond at longer distances, when approached from the shore than when approached from the land or parallel to the shore. This is one of the first reports of sex differences in FIDs for birds, with sex differences only manifesting themselves under certain approach types. Group size, the order of repeated approaches, and time of day did not influence responses, although starting distance of approach was positively related to FID.     

Effects of US 1 Project on Florida Key Deer Mortality

ABSTRACT Approximately 26% of annual mortality for the endangered Florida Key deer (Odocoileus virginianus clavium) occurs as deer-vehicle collisions (DVCs) on the 5.6-km section of United States Highway 1 (US 1) on Big Pine Key (BPK), but extensive urban development adjacent to sections of US 1 complicates efforts to reduce DVCs. Our objective was to evaluate the effectiveness of the US 1 Project (continuous 2.6-km system of 2.4-m fencing, 2 underpasses, and 4 experimental deer guards constructed on US 1 on BPK) in reducing DVCs along US 1. Deer used the underpasses all 3 postproject years (2003–2005); however, we observed higher underpass use in 2004 and 2005 compared to 2003. Exclusion fencing reduced deer intrusions onto the fenced section of US 1 during the 3-year period (2003, n = 7 deer; 2004, n = 4; 2005, n = 12). With a reduction of deer intrusions onto this section of US 1, DVCs decreased in the fenced area by 73–100%; however, US 1 DVCs within the unfenced sections of US 1 also increased (40%) as expected. In controlling for effects of increasing deer density and traffic volume, study results suggest that highway improvements have decreased the net risk of DVCs along US 1, which indicates that use of deer fencing, deer guards, and underpasses is applicable in other urban communities experiencing unacceptable levels of DVCs.     

Scavenging Opportunities Modulate Escape Responses over a Small Geographic Scale

Many species that inhabit anthropogenically altered landscapes also opportunistically use human food refuse. Gulls readily exploit anthropogenic food sources (e.g. rubbish dumps and other places of human refuse) and often ‘steal’ food from people eating out of doors. Their behaviour suggests that gulls perceive little risk around people and so we examined whether opportunity costs, that is access to anthropogenic food sources, influence risk monitoring and escape responses in Silver Gulls (Chroicocephalus novaehollandiae) around outdoor restaurants (‘food’ sites), where the gulls would scavenge food from people. We recorded alert distance (AD) and flight initiation distance (FID) and compared them with nearby sites where the same cohort of gulls was not interacting with people (‘no‐food’ sites). We used two approach speeds (with the prediction that gulls would take greater efforts to avoid a potential predation threat when approached at speed). Gulls foraging at food sites had lower AD and FID than those approached at no‐food sites. They were not simply ignoring the person, as they demonstrated longer AD when approached at speed but no difference in FID and therefore appeared to be responding to a small geographic scale ‘behavioural footprint’ of anthropogenic influences. Our study also challenges universality of the assumption that starting distance is necessarily correlated with FID, especially in sites where there are many people that animals are constantly monitoring – to determine the risk they represent as well as the likelihood of potential food opportunities.     

County-Level Factors Contributing to Deer-Vehicle Collisions in Arkansas

ABSTRACT Arkansas harbors a substantial white-tailed deer (Odocoileus virginianus) population, boasts an expanding human population, and both enjoys and suffers the resulting consequences. A highly visible negative consequence is the occurrence of deer-vehicle collisions (DVCs). Several studies have investigated site-specific factors that may contribute to DVCs. However, few studies have explored the role of broader scale factors. In this study, we used an exploratory, multivariate approach to examine the influence of county-level factors on the density (no./1,000 km) of reported DVCs in Arkansas, USA, during 1998–2001. Factors considered to contribute to DVCs in Arkansas included human and deer population densities, urban growth, various roadway characteristics, daily traffic counts, timber harvests, and landcover composition and spatial characteristics. Using principal components and regression analysis we determined that there were 2 important components contributing to DVC densities in Arkansas. Component 1 represented a predominantly forested matrix with high edge density and contrast. Component 2 described an urban environment, with high road densities, human population densities, and average daily traffic counts. These 2 components were strongly related to DVCs (r² = 0.55, P < 0.001), with component 2 explaining the most variation (71.4%). The identification and recognition of the contribution of these broad-scale factors to DVCs provide insight useful in making informed decisions related to DVC mitigation.     

Flight initiation distance in Lepidopterans is species-specific and positively related to starting distance

Escape behaviour is a critical component of invertebrate life history but is poorly studied. Flight initiation distance (FID) indexes escape propensity, and is well-studied in vertebrates but is entirely unstudied in Lepidopterans, despite their obvious escape behaviour. Here we test two general principles regarding FID as derived from studies of vertebrates to examine if they apply to Sri Lankan butterflies: 1) that FID is a species-specific trait and 2) that FID increases with Starting Distance, the distance at which the experimenter begins an approach. We collected 295 FIDs from 17 species and find that 1) FIDs are a tractable way of indexing butterfly escape and 2) both the general principles tested apply to butterfly escape. We also present FIDs of these species to encourage further data collection and comparative analysis of butterfly escape.     

Flush early and avoid the rush? It may depend on where you stand

Optimal escape theory predicts that animals should flee at an optimal distance from the approaching predator (flight initiation distance, FID). However, FID usually increases with increasing alert distance (AD) or starting distance (SD). As an explanation for this pattern, the “flush early and avoid the rush” (FEAR) hypothesis states that prey should escape soon after detecting an approaching predator due to the cost of continuously monitoring risk. However, the positive relationship observed may also result from a mathematical artefact. Meanwhile, it is unknown whether animals would consistently follow this rule in different environmental contexts. We explored escape behaviours in light-vented bulbuls (Pycnonotus sinensis) perched at different heights. FID generally increased with increasing AD and decreasing perch height. The positive relationships between AD and FID were outside the 95% confidence levels of simulated slopes from Monte Carlo simulations, suggesting that the relationships observed reflect biological effects rather than merely a mathematical artefact. Increasing perch height was also associated with longer buffer distance (defined as FID minus AD or SD), suggesting that the birds tend to delay their flush after detecting an approaching predator when perched high. The effects of environmental contexts (and the associated predation risk) on the AD-FID relationship should be considered when performing inter-specific comparisons or meta-analyses.     

Life history,predation and flight initiation distance in a migratory bird

Life‐history trade‐offs occur as a consequence of the compromise between maximization of different components such as the size and the number of clutches. Flight initiation distance (FID) potentially constitutes a general proximate factor influencing such trade‐offs reflecting the risks that individuals take. Therefore, greater investment in reproduction occurs at a higher risk of death, resulting in selection for efficient flight morphology. I analysed long‐term data on FID in a population of barn swallows Hirundo rustica during 1984–2013 with 2196 records of FID for 1789 individuals. FID had a repeatability of 0.62 (SE = 0.04) and a heritability of 0.48 (SE = 0.07). FID varied between individuals and sites, and it increased over time as climate ameliorated. FID showed a U‐shaped relationship with age, with young and very old individuals having the longest FIDs. Barn swallows that arrived early from spring migration, started to breed early and produced many fledglings had the longest FID. Individuals with the longest tails had the longest FID, and individuals with the shortest aspect ratios and wing loadings had the longest FID. Individuals that died from predation had shorter FID than survivors. These findings are consistent with the hypothesis that FID relates directly to life history, with longer FIDs being associated with smaller levels of risk‐taking.     

Effects of predator behavior and proximity on risk assessment by Columbian black-tailed deer

In predator-prey encounters, many factors influence risk perceptionby prey and their decision to flee. Previous studies indicatethat prey take flight at longer distances when they detect predatorsat longer distances and when the predator's behavior indicatesthe increased likelihood of attack. We examined the flight decisionsof Columbian black-tailed deer (Odocoileus hemionus columbianus)using an approaching human whose speed, directness of approach,directness of gaze, and simulated gun carrying varied. Deerfled at greater distances when approached more quickly and directly,and there was a concave-down quadratic trend in the relationshipbetween the distances at which the predator began its approachand at which the deer became alert (alert distance [AD]), indicatingthat deer have a zone of awareness beyond which there is a delayin detecting an approaching predator. Time spent assessing theapproacher (assessment time) was shorter during faster approachesand was positively related with AD. Deer fled at longer distancesand had shorter assessment times when they were already alertto the predator at the initiation of approach. Males fled atshorter distances than females when approached during the gun-holdingcondition, and males had shorter assessment times than femaleswhen the approacher averted his gaze. Such sex differences inrisk assessment might reflect male motivation during the matingseason as well as exposure to human hunting. We suggest thatrisk assessment is affected the by the predator's behavior,the state of awareness of the prey, and the distance at whichthey detect the predator.     

Animal reactions to oncoming vehicles: a conceptual review

Animal–vehicle collisions (AVCs) are a substantial problem in a human‐dominated world, but little is known about what goes wrong, from the animal's perspective, when a collision occurs with an automobile, boat, or aircraft. Our goal is to provide insight into reactions of animals to oncoming vehicles when collisions might be imminent. Avoiding a collision requires successful vehicle detection, threat assessment, and evasive behaviour; failures can occur at any of these stages. Vehicle detection seems fairly straightforward in many cases, but depends critically on the sensory capabilities of a given species. Sensory mechanisms for detection of collisions (looming detectors) may be overwhelmed by vehicle speed. Distractions are a likely problem in vehicle detection, but have not been clearly demonstrated in any system beyond human pedestrians. Many animals likely perceive moving vehicles as non‐threatening, and may generally be habituated to their presence. Slow or minimal threat assessment is thus a likely failure point in many AVCs, but this is not uniformly evident. Animals generally initiate evasive behaviour when a collision appears imminent, usually employing some aspect of native antipredator behaviour. Across taxa, animals exhibit a variety of behaviours when confronted with oncoming vehicles. Among marine mammals, right whales Eubalaena spp., manatees Trichechus spp., and dugongs Dugong dugon are fairly unresponsive to approaching vehicles, suggesting a problem in threat assessment. Others, such as dolphins Delphinidae, assess vehicle approach at distance. Little work has been conducted on the behavioural aspects of AVCs involving large mammals and automobiles, despite their prevalence. Available observations suggest that birds do not usually treat flying aircraft as a major threat, often allowing close approach before taking evasive action, as they might in response to natural predators. Inappropriate antipredator behaviour (often involving immobility) is a major source of AVCs in amphibians and terrestrial reptiles. Much behavioural work on AVCs remains to be done across a wide variety of taxa. Such work should provide broad phylogenetic generalizations regarding AVCs and insights into managing AVCs.     

Relative vulnerability of chronic wasting disease infected mule deer to vehicle collisions

We estimated chronic wasting disease (CWD) prevalence among vehicle-killed mule deer (Odocoileus hemionus) in select data analysis units (DAUs) in northern Colorado, USA, and compared these with estimated CWD prevalence among mule deer of the same sex sampled in the vicinity of collision sites to assess relative vulnerability of CWD-infected individuals to vehicle collisions. Twenty-five of 171 vehicle-killed mule deer tested positive for CWD (overall prevalence=0.146, 95% confidence interval [CI]=0.097-0.208); 173 of 2,317 deer sampled in the vicinity of these vehicle-killed deer tested positive (overall prevalence=0.075, 95% CI=0.064-0.085). In nine of ten DAU x sex comparisons, relative risk of CWD infection tended to be higher among vehicle-killed deer (range of estimated relative risks=1.6-15.9). Spongiform encephalopathy was detected in 12 of 20 (60%; 95% CI=39-81%) CWD-positive deer killed by vehicles and in 79 of 180 (44%; 95% CI=37-52%) CWD-positive deer detected via random sampling (relative risk=1.37; 95% CI=0.92-2.03), suggesting that infected deer killed by vehicles tended to be in later stages of disease than those killed by hunters. Our data offer evidence that CWD-infected mule deer may be relatively vulnerable to vehicle collisions. It follows that sampling of vehicle-killed mule deer may be exploited to increase efficiency of surveillance programs designed to detect new foci of CWD infection; moreover, evidence of increased susceptibility to vehicle collisions may aid in understanding vulnerability of CWD-infected individuals to other forms of death, particularly predation.     

Inter-individual variability in fear of humans and relative brain size of the species are related to contemporary urban invasion in birds

Background

Urbanization is the most prevailing cause of habitat transformation worldwide, differing from others by its intense levels of human activity. Despite its obvious impact on wildlife, it is still unclear why and how some species are able to adapt to urban settings. One possibility is that fear of humans and vehicles could preclude most species from invading cities. Species entering urban environments might be those that are more tolerant of human disturbance (i.e., tame species). Alternatively or in addition, urban invaders could be a fraction of variable species, with “tame” individuals invading urban habitats and other individuals remaining in rural areas.

Methodology

Using the contemporary urban invasion by birds in a recently established South American city, we tested both hypotheses by relating interspecific differences in invasiveness to their flight initiation distances (i.e., the distances at which birds flee from approaching cars, FID), as well as to their relative brain size (RBS), a correlate of measures of behavioral flexibility.

Principal Findings

Urban invasiveness was not significantly related to species'' average rural FIDs but positively related to their RBS and inter-individual variability in FID. Moreover, FIDs were consistently lower in urban than in rural conspecifics, and the FIDs of urban individuals were within the lower-range distribution of their rural conspecifics. RBS indirectly influenced urban invasion through its positive effect on inter-individual variability in FID.

Conclusions/Significance

Urban invaders do not appear to be individuals from apparently tame species, but rather tame individuals from species with a variable response regarding fear of people. Given the positive relationship between RBS and inter-individual variability in FID, our results suggest that behavioural flexibility should be regarded as a specific trait encompassing variability among individuals. Further research is needed to ascertain the neurophysiological mechanisms underlying the relationship between brain size and inter-individual variability in behavioural traits.     

Island tameness: living on islands reduces flight initiation distance

One of Darwin''s most widely known conjectures is that prey are tame on remote islands, where mammalian predators are absent. Many species appear to permit close approach on such islands, but no comparative studies have demonstrated reduced wariness quantified as flight initiation distance (FID; i.e. predator–prey distance when the prey begins to flee) in comparison with mainland relatives. We used the phylogenetic comparative method to assess influence of distance from the mainland and island area on FID of 66 lizard species. Because body size and predator approach speed affect predation risk, we included these as independent variables. Multiple regression showed that FID decreases as distance from mainland increases and is shorter in island than mainland populations. Although FID increased as area increased in some models, collinearity made it difficult to separate effects of area from distance and island occupancy. FID increases as SVL increases and approach speed increases; these effects are statistically independent of effects of distance to mainland and island occupancy. Ordinary least-squares models fit the data better than phylogenetic regressions, indicating little or no phylogenetic signal in residual FID after accounting for the independent variables. Our results demonstrate that island tameness is a real phenomenon in lizards.     

Does Locomotor Ability Influence Flight Initiation Distance in Yellow‐Bellied Marmots?

Flight initiation distance (FID) is the distance between a potential threat and the point at which a potential prey flees. Animals may modify their FID to compensate for increased risk generated by external/extrinsic factors such as habitat type, visibility, group size, time of year, predator‐approach velocity, and distance to burrow, as well as internal/intrinsic factors such as physical condition, body temperature, crypsis, and morphological antipredator defenses. The intrinsic speed at which an animal can escape a predator is a factor that should influence FID. We studied the relationship between an individual's intrinsic escape speed and FID in yellow‐bellied marmots (Marmota flaviventris) to determine whether marmots compensated for slower escape speeds by fleeing at greater distances. We found no evidence of risk compensation. Rather, we found that slower marmots tolerated closer approaches. This behavioral syndrome may be explained by a coevolution of FID and escape speed in determining an individual's antipredator behavior, an idea upon which we expand.     

Three-dimensional analysis of aphid landing behaviour in the laboratory and field

The final second of the landing approach of black bean aphids, Aphis fabae, was analysed in three dimensions using video techniques. A yellow landing platform was placed upwind or downwind from aphids aggregating under a ceiling light in a laboratory wind tunnel with 10, 20, 30, 40 or 50 cm s^–1 wind speeds, and up-tunnel or down-tunnel in still air. As individual aphids flew to the platform, body orientation (assessed by direct observation) was predominantly into-wind whether the initial flight direction to the landing platform was upwind or downwind. A greater proportion showed into-wind body orientation as wind speed increased. Flight track parameters which differed significantly between wind speeds were the track length, linear start to finish distance, linearity index, horizontal ground speed, speed vertical to the ground, vertical turning rate, and horizontal turning rate. The position of the landing platform was important for track length, linear start to finish distance, horizontal ground speed, three-dimensional turning rate, horizontal turning rate, vertical turning rate, and sinuosity. As wind speed increased above 30 cm s^–1 the ground speed became more consistent and indicated considerable variation in air speed to adjust for ground speed. For the majority of aphids there was a strong preference (88%) for into-wind landings with initial upwind directed flight, while for downwind flights a significant number (55%) of insects reversed initial flight direction and landed into-wind. Field recorded landings showed that 66% of aphids landed into-wind and there was a mean bearing to the wind of 71 ± 42°, a similar finding to wind-tunnel studies.     

The influence of time factors on the dynamics of roe deer collisions with vehicles

Environmentalists and authorities responsible for road safety are trying to reduce the number of wildlife collisions with vehicles (WCV) worldwide. Roe deer are the most common large animal involved in WCV in Europe. This article discusses the distribution of 2010 wildlife-vehicle collisions involving roe deer (WVRD) in Lithuania in 2013 and 2014. The collisions were analyzed in terms of monthly and daily data for each month separately, and the results are compared with the time of sunrise and sunset in Lithuania. By analyzing trends of natural factors that influence the number of collisions we show that the frequency of WVRD is strongly correlated with seasonal and yearly changes in sunrise and sunset. This research shows that these natural factors are extremely important for the dynamics of WVRD. Future analysis of these factors and application of appropriate preventative measures should significantly reduce the risk of collision between vehicles and roe deer.     

Hazard Assessment of Deer–Vehicle Collisions in Michigan

The relationship between deer–vehicle collision counts and vehicle miles traveled (VMT) is studied in this article using the Michigan (USA) crash database and categorized exposure data under different levels of data disaggregation. Negative binomial regression models were developed to establish the association between (human and deer) exposure and the frequency of deer–vehicle collisions. It is shown that VMT is nonlinearly correlated with the collision counts for most sets of circumstances except in rural areas. Observation of the association between the deer–vehicle collision count and the annual VMT across counties in Michigan reveals the unique characteristic of heteroskedasticity (i.e., variances of collision count are amplified with the increasing VMT). The regression results demonstrate that deer density stands out as the most significant exposure predictor in describing deer–vehicle collisions at the state level. It is recommended that differentiated exposure measurements for deer–vehicle collisions should be employed for three ecoregions in Michigan. Exposure predictors for deer–vehicle collisions appear to be more dependent on deer density in Michigan's Upper Peninsula and North Lower Peninsula ecoregions, while in the South Lower Peninsula ecoregion deer and human populations are equally important.