habitat choice

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Blog - Bioenergetics for management and conservation
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    • When a macaque has the choice between two lianasby Marie Delbasty and Julie Viana

      Published by Charlotte Recapet the May 10, 2021 on 8:00 AM

      Two populations of moor macaques (Macaca maura) were studied in their natural environment in South Sulawesi, Indonesia in order to understand their use of two different habitats in karst forest.

      Moor macaque is a species currently classified as "endangered" by the IUCN, mainly due to the disturbance and fragmentation of its habitat. That is why, in order to develop adequate conservation plans and management strategies, it is essential to study the patterns of habitat use in relation to the distribution of essential food resources.

      Concerning the two types of habitat, they were characterized according to the vegetation present and its abundance as well as the topography and the presence of any trace of human activity.

      The two habitats of this forest are in fact distinguished in two essential aspects:

      The forest situated at the highest altitude with a steep slope, has few food resources but is not accessible to humans

      vs.

      The gently sloping forest, rich in resources but frequented by humans.

      In order to carry out this study, each group of macaques was observed after having been accustomed to the presence of the scientists. The largest group consisted of about 30 individuals while the smallest group consisted of 18 macaques. The behaviour of the smallest group was studied from June to November 2016 while the largest group was studied from September 2014 to February 2015. Behavioural activities were defined as feeding, foraging, locomotion, social interactions and resting.

      Although both habitats are used on a daily basis by each population, the analysis revealed that for both groups, the only behaviour that differed primarily between the two habitat types was time spent feeding. They spent more time feeding in the more food-rich forest habitat. The larger group spent more time overall in the food-rich forest while the smaller group spent more time in the food-poor forest.

      The habitat with fewer resources is more of a refuge area for the macaques as they have no real predators and humans are the main threat. The larger group's use of a more productive but riskier habitat may be due to its history of provisioning, which may have allowed its individuals to have less fear of encountering humans. On the other hand, the individuals of the other group have never experienced provisioning. Another possible explanation is group size. Indeed, individuals in the larger group have less need to be vigilant because of their numbers, compared to the smaller group. In addition, the larger group might dominate the other group from a competitive point of view and thus be given priority for benefiting from resources.

      In this context, macaques seem to be ecologically flexible, able to exploit the karst forest as a whole and to cope with human disturbance. It is important to protect the forest to allow the species to persist as habitat fragmentation threatens its survival. Thus, the management of this area would consist of balancing the needs of humans and macaques, and one of the solutions could be to educate local people on the protection of the species.

      In a global context of loss of many species, the ideal would be to be able to leave in peace those for whom this is possible. Indeed, it seems preferable not to allow humans to access this area for the good of these macaques especially since this area is probably home to most of the remaining populations. Indeed, forest habitat with more food resources is a crucial part of the landscape for the survival of moor macaques in southern Sulawesi.

      Thus, a question then arises:

      would it be possible to let these macaques enjoy their habitats in peace while moving from one liana to another like Tarzan and Jane? To be continued…

      Read the full study: Albani A., Cutini M., Germani L., Riley E. P., Oka Ngakan P. and Carosi M. (2020) Activity budget, home range, and habitat use of moor macaques (Macaca maura) in the karst forest of South Sulawesi, Indonesia. Primates 61, 673–684 (https://doi.org/10.1007/s10329-020-00811-8).

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    • Can bioenergetic models help the re-introduction of the native Rio Grande cutthroat trout in a Southwestern headwater stream?by Emmanuel Bourgoin and Aurélien Callens.

      Published by Charlotte Recapet the May 16, 2018 on 1:47 PM

      Re-introduction of native species is far from being simple: many parameters must be accounted for! To illustrate that, we are going to take a closer look at a study made by Kalb and Huntsman (2017) on a stream in southcentral New Mexico which was deemed suitable for re-introduction of the native Rio Grande cutthroat trout (Oncorhynchus clarkii virginalis). Before re-introducing this species, researchers wanted to know if the habitat was able to sustain it. Thus, they evaluated habitat using resource selection functions with a mechanistic drift-foraging model to explain rainbow trout distributions. They studied rainbow trouts because they are present on the stream and are close relative to the Rio grande cutthroat trout, consequently all the results of this study can be extended to this native species.

       
      Rainbow trout - Timothy Knepp/U.S. Fish and Wildlife Service - Public domain

      Each month, the available habitat and foraging locations were evaluated along the stream. Foraging locations were defined as the location where they could observe a foraging fish. For each foraging site, the length of the fish was estimated and physical characteristics such as discharge, focal velocity (current velocity at the head of the fish), depth, cover distance and temperature were measured on the exact fish location. These parameters were also measured on the available sites. Macroinvertebrate drift was estimated on all the locations (available and foraging). All these parameters were used in bioenergetic models which allow the researchers to estimate all the intakes of the fish (net energy intake, energy assimilated…) and all the costs associated with foraging (capturing a prey, swimming…).

      First, they observed that macroinvertebrate drift was strongly season- and temperature-dependant with high values in summer and fall and low values in winter and spring. Moreover, as we must expect it, water temperature, depth and discharge were found to be seasonal parameters too. Secondly, models identified the depth as the most limiting factor for habitat selection: trout of all ages preferred habitat location with a greater depth.  The most interesting thing about the models is that they can show the characteristics of the chosen habitat according to the age of the trout and the season. In fact, they showed that during the winter the smaller size-classes were more likely to choose a position closer to cover. Additionally, they highlighted that spring was the season with the greater energy intake for all the size-classes expect the 4+. Finally, drift-foraging models identified that 81% of observed trout selected positions could meet maintenance levels throughout the year and 40% of selected habitats could sustain maximum growth. Despite these last observations, the larger size-classes were energetically more limited throughout the year.

      This study showed that trout population prefers deep pool habitats with slow moving water and that this stream was able to sustain a great population of rainbow trout and could consequently sustain a great native population of Rio grande cutthroat trout. However, authors warn us about the risk of hybridization and interspecific competition and suggest removing the non-native fishes first.

      To answer the question in the title: yes, bioenergetic models can help to re-introduce a native species in a given environment. Nonetheless, this example is really specific: author had the chance to find and study a close relative to the native trout in the stream! The main thing to remember is that bioenergetic models give a lot of useful information on how a species uses an habitat and must be taken into account (if applicable) in the management of species.

      Cited study : Kalb, B. W., Huntsman, B. M., Caldwell, C. A., & Bozek, M. A. (2018). A mechanistic assessment of seasonal microhabitat selection by drift-feeding rainbow trout Oncorhynchus mykiss in a Southwestern headwater stream. Environmental Biology of Fishes, 101(2), 257-273.

       

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