Summary1. Radiotelemetry and satellite-based telemetry approaches are essential to describe the behaviour and biology of animals. This is especially true for bats, whose small size and cryptic lifestyles make them challenging to study. However, only a handful of studies have evaluated how transmitter mass and the attachment method affect bat behaviour or health, and none have assessed the development of technical methods in the field. 2. We review the past 50 years of bat tracking studies to determine how devices have been attached, how guidelines have been followed or changed, and whether any health or fitness impacts from these transmitters can be determined. 3. Half of the nearly 300 studies available used devices heavier than the recommended 5% of body mass with minimal justification. Devices were typically glued directly to the backs of small bats and remained attached for 9 days. This is far shorter than battery life span of most devices. Little information is available regarding the overall impact of attaching transmitters on the health, survival and reproductive success of bats, and there has been little development in attachment methods since the first tracking studies. 4. We consequently developed a collar for small bats with a degradable weak link and tested it on several species. The collar worked successfully on three of four species. This allows longer habituation and tracking times while ensuring that the device drops off after the battery expires. 5. Future studies will need to invest more effort in assessing potential long-term effects of tracking. They also need to build upon previous knowledge to find the best attachment method, size and shape for their study species to effectively improve wildlife tracking.

Bat immune systems may allow them to respond to zoonotic agents more efficiently than other mammals. As the first line of defence, the taxonomically conserved acute phase immune reaction of leucocytosis and fever is crucial for coping with infections, but it is unknown if this response is a key constituent to bat immunological success. We investigated the acute phase reaction to a standard lipopolysaccharide (LPS) challenge in Pallas's mastiff bats ( Molossus molossus ). Challenged bats lost mass, but in contrast to other mammals showed no leucocytosis or fever. There also was no influence on body temperature reduction during torpor. When compared to recent genome-wide assays for constituent immune genes, this lack of a conserved fever response to LPS contributes to a clearer understanding of the innate immune system in bat species and of the coevolution of bats with a wide diversity of pathogens.

Migratory decisions in birds are closely tied to environmental cues and fat stores, but it remains unknown if the same variables trigger bat migration. To learn more about the rare phenomenon of bat migration, we studied departure decisions of female common noctules (Nyctalus noctula) in southern Germany. We did not find the fattening period that modulates departure decisions in birds. Female noctules departed after a regular evening foraging session, uniformly heading northeast. As the day of year increased, migratory decisions were based on the interactions among wind speed, wind direction and air pressure. As the migration season progressed, bats were likely to migrate on nights with higher air pressure and faster tail winds in the direction of travel, and also show high probability of migration on low-pressure nights with slow head winds. Common noctules thus monitor complex environmental conditions to find the optimal migration night.

Long-distance migration is a rare phenomenon in European bats. Genetic analyses and banding studies show that females can cover distances of up to 1,600 km, whereas males are sedentary or migrate only short distances. The onset of this sex-biased migration is supposed to occur shortly after rousing from hibernation and when the females are already pregnant. We therefore predicted that the sexes are exposed to different energetic pressures in early spring, and this should be reflected in their behavior and physiology. We investigated this in one of the three Central European long-distance migrants, the common noctule (Nyctalus noctula) in Southern Germany recording the first individual partial migration tracks of this species. In contrast to our predictions, we found no difference between male and female home range size, activity, habitat use or diet. Males and females emerged from hibernation in similar body condition and mass increase rate was the same in males and females. We followed the first migration steps, up to 475 km, of radio-tagged individuals from an airplane. All females, as well as some of the males, migrated away from the wintering area in the same northeasterly direction. Sex differences in long-distance migratory behavior were confirmed through stable isotope analysis of hair, which showed greater variation in females than in males. We hypothesize that both sexes faced similarly good conditions after hibernation and fattened at maximum rates, thus showing no differences in their local behavior. Interesting results that warrant further investigation are the better initial condition of the females and the highly consistent direction of the first migratory step in this population as summering habitats of the common noctule occur at a broad range in Northern Europe. Only research focused on individual strategies will allow us to fully understand the migratory behavior of European bats.

The ability to discriminate information quality from multiple social partners may be essential to animals that use social cues in deciding when, where, and what to eat. This may be particularly important in species that rely on ephemeral and widely dispersed resources. We show that tent-making bats, Uroderma bilobatum, socially acquire preferences for novel foods through interactions with roostmates both in captivity and in natural roosts and that these food cues can influence roostmates' decisions at least for several days. More importantly, these bats can distinguish between the quality and information content of 2 different cues that are brought back to their roost. Inexperienced individuals prefer food that has been consumed by a roostmate to food whose odor is present only on the fur of a roostmate that has eaten sugar water. The ability of bats to discriminate odors on breath and fur may allow them to select the most infonnative cues about the presence or renewed availability of dispersed resources. This selectivity may help stabilize roosts as information centers for the social acquisition of updated information on unpredictable and widely distributed food items.

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Active flight requires the ability to efficiently fuel bursts of costly locomotion while maximizing energy conservation during non-flying times. We took a multi-faceted approach to estimate how fruit-eating bats (Uroderma bilobatum) manage a high-energy lifestyle fueled primarily by fig juice. Miniaturized heart rate telemetry shows that they use a novel, cyclic, bradycardic state that reduces daily energetic expenditure by 10% and counteracts heart rates as high as 900 bpm during flight. Uroderma bilobatum support flight with some of the fastest metabolic incorporation rates and dynamic circulating cortisol in vertebrates. These bats will exchange fat reserves within 24 hr, meaning that they must survive on the food of the day and are at daily risk of starvation. Energetic flexibly in U. bilobatum highlights the fundamental role of ecological pressures on integrative energetic networks and the still poorly understood energetic strategies of animals in the tropics.

Three fundamental ontogenetic pathways lead to the development of size differences between males and females. Males and females may grow at the same rate for different durations (bimaturism), grow for the same duration at different rates, or grow at a mix of rate and duration differences. While patterns of growth and the development of adult body size are well established for many haplorhines, the extent to which rate and duration differences affect strepsirrhine growth trajectories remains unclear. Here, we present iterative piecewise regression models that describe the ontogeny of adult body mass for males and females of five lorisoid species (i.e., lorises and galagos) from the Duke Lemur Center. We test the hypotheses that, like most haplorhines, sexual size dimorphism (SSD) is a result of bimaturism, and males and females of monomorphic species grow at the same rate for a similar duration. We confirm that the galagos in this sample (Galago moholi and Oto lemur garnettii) show significant SSD that is achieved through bimaturism. Unlike monomorphic lemurids, the lorises in this sample show a diversity of ontogenetic patterns. Loris tardigradus does follow a lemur-like trajectory to monomorphism but Nycticebus coucang and Nycticebus pygmaeus achieve larger adult female body sizes through a mixture of rate and duration differences. We show that contrary to previous assumptions, there are patterns of both similarity and difference in growth trajectories of comparably sized lorises and galagos. Furthermore, when ontogenetic profiles of lorisoid and lemurid growth are compared, it is evident that lorisoids grow faster for a shorter period of time. Strepsirrhine primates show variable degrees of sexual size dimorphism (SSD), but the ontogenetic processes that generate this variation have only been explored in the monomorphic lemurids (Leigh and Terranova, 1998). Counter to the typical mammalian pattern of SSD (Rensch, 1959), the largest living strepsirrhine species (Indri indri) and the large, extinct subfossil lemurs show little to no SSD (Godfrey et al., 1993), likely as a result of identical male and female growth trajectories (Godfrey et al., 1993;Leigh and Terranova, 1998). However, it is in the smallest bodied strepsirrhine species that the greatest SSD is found. These species show both male and female biased SSD, as well as strong seasonal fluctuations in the degree to which dimorphism is expressed (Kappeler, 1990;Schmid and Kappeler, 1998), but the growth processes that produce these levels of SSD have not yet been described.In this article, we explore the ontogeny of adult body mass and SSD in galagos and lorises. We use the Lorisoidea taxonomy of Grubb et al. (2003) wherein galago species are placed into a single family, the Galagidae, and the lorises and pottos are placed into the Lorisidae. We refer to these groups as galagos and lorises, respectively, and collectively as lorisoids. We test the hypotheses that: 1) like most anthropoids, SSD in galagos is a result of differences in the duration o...