Camera traps have proven very useful in ecological, conservation and behavioral research. Camera traps non-invasively record presence and behavior of animals in their natural environment. Since the introduction of digital cameras, large amounts of data can be stored. Unfortunately, processing protocols did not evolve as fast as the technical capabilities of the cameras. We used camera traps to record videos of Eurasian beavers (Castor fiber). However, a large number of recordings did not contain the target species, but instead empty recordings or other species (together non-target recordings), making the removal of these recordings unacceptably time consuming. In this paper we propose a method to partially eliminate non-target recordings without having to watch the recordings, in order to reduce workload. Discrimination between recordings of target species and non-target recordings was based on detecting variation (changes in pixel values from frame to frame) in the recordings. Because of the size of the target species, we supposed that recordings with the target species contain on average much more movements than non-target recordings. Two different filter methods were tested and compared. We show that a partial discrimination can be made between target and non-target recordings based on variation in pixel values and that environmental conditions and filter methods influence the amount of non-target recordings that can be identified and discarded. By allowing a loss of 5% to 20% of recordings containing the target species, in ideal circumstances, 53% to 76% of non-target recordings can be identified and discarded. We conclude that adding an extra processing step in the camera trap protocol can result in large time savings. Since we are convinced that the use of camera traps will become increasingly important in the future, this filter method can benefit many researchers, using it in different contexts across the globe, on both videos and photographs.

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12Activity patterns play an important role in the fitness of animals. Energy conservation, 13 physiological adaptations, prey availability, competition, and predation caused by predators 14 and humans are all important parameters influencing when, and where, animals are active. 15 Over time, however, a change in such external factors can lead to a shift in optimal activity 16 patterns. In this paper, we use camera traps to study the daily activity patterns of Eurasian 17 beavers (Castor fiber) reintroduced into an atypical, predator-free landscape. We explore if 18 and how beavers have adjusted their activity patterns in the absence of predators, and whether 19 this varies with day length and moonshine. Our results reveal that beavers in our study area 20 have a mainly crepuscular and nocturnal activity pattern, similar to animals in more natural 21 landscapes with predators. Changes in day length had only a limited effect on the duration of 22 beavers' activity, but, contrary to our expectations, beaver activity increased during bright 23 moonlight. Activity patterns were also clearly bimodal during nights with bright moonlight, 24 but unimodal during dark nights. The shape of their activity pattern did change throughout the 35 The timing of activity is crucial for most animals. Temporal changes in activity (hereafter 36 activity patterns) are an important adaptation that evolved in response to the time structure of 37 the environment, which changes with a 24 h periodicity. Activity patterns allow an animal to 38 anticipate the right time for a given behaviour or activity (Roll et al., 2006) and are influenced 39 by a number of factors, including an animal's physiological adaptations, prey availability and 40 distribution, competition, and disturbances caused by predators and humans (Kitchen et al., 41 2000; Yerushalmi and Green, 2009). There is evidence that the evolutionary arms race 42 between predators and prey for temporal niche occupation may have led to considerable 43 adaptive plasticity in temporal niche usage among even the earliest mammals (Hut et al., 44 2012). 45 46Plasticity in activity patterns has also been observed in a range of modern mammals, often 47 because of changes in the intensity of predation or competition, and over varying time scales. 48Svalbard reindeer (Rangifer tarandus platyrhynchus), isolated from predators for more than 49 5000 years, have no distinct peaks in activity at sunrise and sunset. This is expected for 50 animals maximizing energy intake rates in predator-free environments (Loe et al., 2007). 51Changes in behaviour and activity patterns in response to external cues have also been 52 recorded within shorter time spans. A coyote (Canis latrans) population that had historically 53 been exposed to human persecution shifted to higher levels of diurnal activity less than eight 54 years after persecution ceased (Kitchen et al., 2000). On an even shorter time scale, Fenn and 55 MacDonald (1995) observed diurnal activity in normally nocturnal wild rats (Rattus 56 nor...

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Beavers are known for their ability to build dams that change the environment. They also occupy territories where they do not construct dams. The goal of this study was to determine which environmental factors influence beaver dam construction and to examine the upstream water level increase caused by the dams. We compared factors collected at 15 beaver territories with dams (32 dams) and 13 territories without dams (i.e., control) in the gently undulating and human-dominated landscape of Middle Belgium in 2013. River width, river depth, distance from woody vegetation, stream velocity, and bank height differed significantly between territories with and without dams. Water depth was the most important parameter to correctly classify territories as either dam territory or control territory (with 97% accuracy). When beavers were present and water depth in summer was <68 cm, the probability of dam building was high; if water depth was >68 cm, dam building was unlikely. Dams caused an increase in the upstream water level of on average 47 AE 21 cm. On average the water level could rise only an additional 25 AE 30 cm upstream of the dam before bank overtopping would occur. These results provide a simple tool for planners to assess the probability of floodplain inundation by beaver dam building, as part of multifunctional riverine landscape management. Ó 2018 The Wildlife Society.