Sergio A. Lambertucci

Energy Landscapes Shape Animal Movement Ecology

The metabolic costs of animal movement have been studied extensively under laboratory conditions, although frequently these are a poor approximation of the costs of operating in the natural, heterogeneous environment. Construction of “energy landscapes,” which relate animal locality to the cost of transport, can clarify whether, to what extent, and how movement properties are attributable to environmental heterogeneity. Although behavioral responses to aspects of the energy landscape are well documented in some fields (notably, the selection of tailwinds by aerial migrants) and scales (typically large), the principles of the energy landscape extend across habitat types and spatial scales. We provide a brief synthesis of the mechanisms by which environmentally driven changes in the cost of transport can modulate the behavioral ecology of animal movement in different media, develop example cost functions for movement in heterogeneous environments, present methods for visualizing these energy landscapes, and derive specific predictions of expected outcomes from individual- to population- and species-level processes. Animals modulate a suite of movement parameters (e.g., route, speed, timing of movement, and tortuosity) in relation to the energy landscape, with the nature of their response being related to the energy savings available. Overall, variation in movement costs influences the quality of habitat patches and causes nonrandom movement of individuals between them. This can provide spatial and/or temporal structure to a range of population- and species-level processes, ultimately including gene flow. Advances in animal-attached technology and geographic information systems are opening up new avenues for measuring and mapping energy landscapes that are likely to provide new insight into their influence in animal ecology.

Turn costs change the value of animal search paths

The tortuosity of the track taken by an animal searching for food profoundly affects search efficiency, which should be optimised to maximise net energy gain. Models examining this generally describe movement as a series of straight steps interspaced by turns, and implicitly assume no turn costs. We used both empirical- and modelling-based approaches to show that the energetic costs for turns in both terrestrial and aerial locomotion are substantial, which calls into question the value of conventional movement models such as correlated random walk or Lévy walk for assessing optimum path types. We show how, because straight-line travel is energetically most efficient, search strategies should favour constrained turn angles, with uninformed foragers continuing in straight lines unless the potential benefits of turning offset the cost.

Energy Beyond Food: Foraging Theory Informs Time Spent in Thermals by a Large Soaring Bird

Current understanding of how animals search for and exploit food resources is based on microeconomic models. Although widely used to examine feeding, such constructs should inform other energy-harvesting situations where theoretical assumptions are met. In fact, some animals extract non-food forms of energy from the environment, such as birds that soar in updraughts. This study examined whether the gains in potential energy (altitude) followed efficiency-maximising predictions in the worlds heaviest soaring bird, the Andean condor (Vultur gryphus). Animal-attached technology was used to record condor flight paths in three-dimensions. Tracks showed that time spent in patchy thermals was broadly consistent with a strategy to maximise the rate of potential energy gain. However, the rate of climb just prior to leaving a thermal increased with thermal strength and exit altitude. This suggests higher rates of energetic gain may not be advantageous where the resulting gain in altitude would lead to a reduction in the ability to search the ground for food. Consequently, soaring behaviour appeared to be modulated by the need to reconcile differing potential energy and food energy distributions. We suggest that foraging constructs may provide insight into the exploitation of non-food energy forms, and that non-food energy distributions may be more important in informing patterns of movement and residency over a range of scales than previously considered.

Dealing with non-native species: what makes the difference in South America?

Non-native species have reached South American ecosystems and may be threatening the exceptional biodiversity of this region. However, people often value and exploit introduced species not knowing that they are non-natives, nor understanding their impacts. In this paper we analyze the trend of scientific research on introduced species in South America and whether a socio-cultural explanation could underlie the results by comparing them with European, North American and Australasian countries. We also controlled for research effort, which could reflect economic inequalities, by analyzing the articles published on introduced species in relation to the total number of articles published on related disciplines. Research trends suggest that non-native species are not of major concern for South American countries, there being less research on this topic in countries with higher biodiversity. Compared to other colonized countries such as the USA, New Zealand and Australia, research on non-native species was lagging and less abundant in South America, even when controlling for research effort. Historical and recent socio-cultural particularities may explain the similar attitudes and research input seen in South American countries and their Spanish and Portuguese colonizers. A generational amnesia, where younger generations descendent from European colonizers are not aware of past biological conditions, could be exacerbating this lack of concern. South American policies seem to reflect the low level of interest in non-native species shown by their citizens. National policies are poorly developed and mainly deal with alien species threatening productive systems. Given the strong cultural component of this dilemma, integrated ways to reverse this situation are needed, including education, international research collaboration, and a common South American policy.

Size and spatio-temporal variations of the Andean condor Vultur gryphus population in north-west Patagonia, Argentina: communal roosts and conservation

Estimations of the population sizes of threatened species are fundamental for conservation. The current estimate of the population of the Andean condor Vultur gryphus is based on limited local counts. Simultaneous censuses of 10 condor communal roosts were therefore conducted during 2006-2008 in north-west Patagonia, Argentina, to obtain a minimum population number, to estimate the size of the local population, and to describe use of the roosts by season and age classes. I fitted the data to two asymptotic models to calculate the population of condors as a function of the number of communal roosts surveyed. In an area of c. 6,300 km 2 I obtained a minimum population size of 246 individuals by direct observation, and a population estimate of 296 condors (range 260-332) by applying the models. This population, the largest known of this species, comprises 68.5% adults and 31.5% imma- tures. Condors had large aggregations in some communal roosts and used the area seasonally, increasing in numbers from autumn to spring and decreasing in summer. Long- term monitoring of communal roosts across the Andean condors range is essential for the monitoring of this rare and vulnerable species.

Protecting Invaders for Profit

Humans have spread species to nonnative environments for generations. In turn, these species can become invasive, threatening native species. There has been much discussion about the best way to control invasive species and protect native species ([ 1 ][1]). However, one point has been overlooked:

Human-wildlife conflicts in a crowded airspace

How can the ecological consequences of the increasing use of airspace by humans be minimized? Over the past century, humans have increasingly used the airspace for purposes such as transportation, energy generation, and surveillance. Conflict with wildlife may arise from buildings, turbines, power lines, and antennae that project into space and from flying objects such as aircrafts, helicopters, and unmanned aerial vehicles (UAVs, or drones) (see the figure) (1–3). The resulting collision and disturbance risks profoundly affect species ecology and conservation (1, 4, 5). Yet, aerial interactions between humans and wildlife are often neglected when considering the ecological consequences of human activities.

From daily movements to population distributions: weather affects competitive ability in a guild of soaring birds.

The ability of many animals to access and exploit food is dependent on the ability to move. In the case of scavenging birds, which use soaring flight to locate and exploit ephemeral resources, the cost and speed of movement vary with meteorological factors. These factors are likely to modify the nature of interspecific interactions, as well as individual movement capacity, although the former are less well understood. We used aeronautical models to examine how soaring performance varies with weather within a guild of scavenging birds and the consequences this has for access to a common resource. Birds could be divided broadly into those with low wing loading that are more competitive in conditions with weak updraughts and low winds (black vultures and caracaras), and those with high wing loading that are well adapted for soaring in strong updraughts and moderate to high winds (Andean condors). Spatial trends in meteorological factors seem to confine scavengers with high wing loading to the mountains where they out-compete other birds; a trend that is borne out in worldwide distributions of the largest species. However, model predictions and carcass observations suggest that the competitive ability of these and other birds varies with meteorological conditions in areas where distributions overlap. This challenges the view that scavenging guilds are structured by fixed patterns of dominance and suggests that competitive ability varies across spatial and temporal scales, which may ultimately be a mechanism promoting diversity among aerial scavengers.

Large-Scale Age-Dependent Skewed Sex Ratio in a Sexually Dimorphic Avian Scavenger

Age-dependent skewed sex ratios have been observed in bird populations, with adult males generally outnumbering females. This trend is mainly driven by higher female mortality, sometimes associated with anthropogenic factors. Despite the large amount of work on bird sex ratios, research examining the spatial stability of adult sex ratios is extremely scarce. The Andean condor (Vultur gryphus) is the only bird of prey with strong sexual dimorphism favouring males (males are 30% heavier than females). By examining data from most of its South-American range, we show that while the juvenile sex ratio is balanced, or even female-skewed, the sex ratio becomes increasing male-skewed with age, with adult males outnumbering females by >20%, and, in some cases by four times more. This result is consistent across regions and independent of the nature of field data. Reasons for this are unknown but it can be hypothesized that the progressive disappearance of females may be associated with mortality caused by anthropogenic factors. This idea is supported by the asymmetric habitat use by the two sexes, with females scavenging in more humanized areas. Whatever the cause, male-skewed adult sex ratios imply that populations of this endangered scavenger face higher risks of extinction than previously believed.

Poisoning People and Wildlife with Lead Ammunition: Time to Stop

The high toxicity of lead has been well-known for centuries, however it continues to threaten wildlife and humans (1). Although several countries have banned the use of different forms of this metal (e.g., in gasoline, paint, etc.) to protect human lives (1, 2), lead ammunition continues to impact wildlife, mainly affecting waterfowl, which ingest lead pellets, causing thousands of deaths annually, and threatening endangered species (1). While several countries of the European Union and EU members have banned the use of lead ammunition in wetlands, similar restrictions are rarely applied in terrestrial ecosystems (3) where avian scavengers, some of them critically endangered, are now menaced by lead toxicity (4). This problem goes beyond the conservation of birds though, because game meat becomes part of the human diet (5). Animals shot with lead projectiles are consumed all over the world, not only by hunters and local people, but also via export and sold in markets (2). The main producers of game meat are New Zealand, UK, Canada, the United States, and the rest of the EU. Main consumers of this food are Germany, Switzerland, France, the U.S., and Asiatic countries. In the EU alone, around 6,571,000 hunters fire more than 40,000 tons of metal pellets (mainly lead) per year (3). This lead, which is also deposited on the ground and water, may remain in the body of game as bullet fragments and can be ingested by humans and wildlife (5). As one of multiple worldwide examples, in the southern tip of South America exotic species such as red deer (Cervus elaphus) and wild boar (Sus scrofa) are increasingly being used in Patagonian restaurants, and those species are generally obtained by hunting. Moreover, millions of European hares (Lepus europaeus) are hunted in Patagonia every year using lead bullets, for the purpose of exporting their meat. Between 1976 and 1979 Argentina exported to Europe more than 13 million kg of hare meat per year, and currently more than two million individuals per year are sold to Europe, mainly Germany, Holland, Belgium, Italy, France, and Switzerland. During the hunting season, a portion of shot individuals do not die immediately, but escape and die later in the field where they are available for scavengers (1, 4). Accordingly, people and fauna consuming game meat in several countries of the world may be exposed to lead (4, 5). Despite the proven consequences for humans of lead ingestion, policies are lacking. Consumption of game meat can increase lead levels in the blood, particularly in children (1). Although regulations for lead meat contamination in the EU apply to livestock (eg., cattle, sheep, pigs, and poultry), game meat is exempt (2). This is partly a consequence of cultural practice, and is an extremely serious problem (3). However, a regulation from the EU, for exampleswhich imports large quantities of game meat, promotes this hunting, and consumes this meatscould be extremely helpful. A legislation demanding game meat free of lead by using nontoxic alternative ammunition would transform the situation for both wildlife in those countries where game is hunted and for citizens who consume this meat. A serious evaluation of the origin and quantity of game food consumed by each country of the world must be done. It could also add up if consumers demand game meat hunted with alternative bullets, and if hunters adopt conscious practices. Those relatively simple actions will help to definitively ban lead ammunition, and would protect both human and wildlife health.