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    • Water, a limiting factor in lizard activities and distributionby Alice Loubet-Laouina

      Published by Charlotte Recapet the June 28, 2021 on 3:32 PM

      Water is an increasingly scarce resource for us, so we can ask ourselves: When will it be for animals? How will they react: flee, adapt, evolve?

      Predicting the effects of climate change on biodiversity is an ecological objective in conservation management. Here we are interested in water restriction role on activities and distribution on ectotherms with the mechanistic niche model.

      Who am I


      Photograph by Olivier Cardona, 2013
      My name is Tiliqua rugosa or Sleepy lizard.

      I am an ectotherm. I explain: I don't produce heat, so I need the sun to warm me up.

      I live in Australia.

      I measure 40 to 45 mm.

      I live for 50 years in the wild!

      I love to eat flowers, fruits, and the leaves of annual plants.

      I can lose more than 70% of my body water despite being adapted to the desert.

      What is a mechanistic niche model?

      So, the study scientists use this model with environmental and biological data of the Tiliqua rugosa. These data create Microclimate and Animal models. This allows us to understand how climate change affected species with a complex life cycle. This model makes it possible to make predictions on the distribution of animals. The same scientists used this method for another study (Enriquez-Urzelai et al. 2019).

      Biological activities

      When we talk about the biological cycle, we are talking about growth and reproduction activities. These activities require energy. Organisms have to make a trade-off between spending and storing energy.

      The consequences of water restriction

      When lizards only have access to water through their food or rainfall, their activities are reduced to the maximum to limit their dehydration and keep their energy. So Sleepy lizards hide in their burrows. They nest in a burrow up to 60 cm deep.

      Water is a limiting factor in reproduction. According to two simulations, lizards reproduce little in the center and northeast of Australia.


      Estimation of net reproductive rate

      Climate change

      To predict long-term evolution, we can use general circulation models in combination with mechanistic niche models. Therefore, it is interesting to compare different scenarios. Scenarios of the general circulation model1 can complement our niche model.

      For the most part, water restriction is not a limiting factor for lizards. By running six scenarios under the assumption of water restriction, we find that the reproduction rate remains constant within the current ranges. The ACCESS 1.3 and GDFLCM3 Scenarios are exceptions.


      Estimation of different scenarios

      Species will be affected by climate change because it will depend on future precipitation patterns. Global warming could therefore cause increased dehydration regardless of rainfall variations.

      1 General circulation model: statistics of several environmental factors allowing to make predictions according to different scenarios developed by countries.

      Read the full study: Kearney, M.R., Munns, S.L., Moore, D., Malishev, M. and Bull, C.M. (2018). Field tests of a general ectotherm niche model show how water can limit lizard activity and distribution. Ecol Monogr, 88: 672-693. https://doi.org/10.1002/ecm.1326

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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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    • Why should we think about cougars when planning our cities?by Amaïa Lamarins and Gautier Magné

      Published by Charlotte Recapet the February 3, 2020 on 2:02 PM


      A puma family above the nighttime lights of San Jose - National Geographic - (photo courtesy of Chris Fust)

      Humans have modified 75% of earth land surface which has important consequences on wildlife. In fact, human presence and activities are perceived as a threat by animals which adapt their behaviors to avoid it. Gaynor and his collaborators’ meta-analysis showed that many species are modifying their daily activities and identified 117 diurnal mammals becoming more and more active at night. Consequently, these animals face constrained access to resources and are susceptible to shifting their diet to nocturnal prey. Thus, anthropic activities influence growth, breeding, survival and community interactions of wild animals.

       
      Shift in rhythmic activity of diurnal species due to human disturbance - Ana Benítez-López.

      In southern California, the habitat of cougars, an apex nocturnal predator, is reduced by the expansion of cities. No, we’re not talking about the rampant nightclub predators (whose habitats remain undisturbed), we’re talking about mountain lions! You’ve probably already heard about pumas roaming across big cities like Santa Cruz, California. They likely are not curious tourists hoping to take in the sites, but are rather disturbed by human activities, which cause their nighttime activity to be higher in developed areas than in natural ones. This shift increases their daily energy expenditure: because of humans, pumas need to eat around 160-190 kg of additional meat per year (for females and males, respectively)! Are there sufficient deer populations to meet these needs? Unfortunately, it seems not, since a significant number of puma attacks on cattle have been recorded.

      These results, showing human-induced behavioral change for pumas, come from a recent study published by members of the Santa Cruz puma project. By wide-scale monitoring of 22 wild pumas, they were able to link their behavior with their subsequent energetic expenditures: pumas’ behavior and movement were measured through spatial GPS location data, recorded every 15min, and energetic cost of movement was estimated considering their weight and travel velocity. An interesting methodological point to note: in order to avoid underestimating the energy expenditures via GPS tracking, scientists calibrated their estimations using accelerometers. Thanks to these methods they figured out the effect of housing densities on pumas’ activity and energetic costs, taking into consideration the time of day and sex of the animal.

      Indeed, they were right in taking into account these factors because, according to their findings, response to human activities differs between day and night and between males and females. During the day pumas are more likely to stay inactive, especially near urban areas. At night, being close to houses increases time spent active by 8.8% and 5.8%, respectively, for males and females. Consequently, estimated daily caloric expenditure increases by 11.6% for males and 10.1% for females in high housing density areas. Below you will find an outline summarizing these results:


      Urban development negatively affects pumas by increasing nighttime activity and energy expenditure.

      Such studies underline the role of bioenergetics to estimate the costs of human-induced behavioral changes but do not provide insight on global energetic allocation. Further work is needed to understand the consequences of energetic balance disturbances and identify which individual functions are affected (growth, maintenance, maturation or reproduction). Besides, human impact could be underestimated because such tracking doesn’t allow us to know if pumas get all available energy from their prey near humans; some observations reported they often have to leave their prey because they fear humans. This partial feeding would constrain pumas to hunt more prey!

      Unfortunately, this is not the only human-induced threat affecting pumas. In the region of Santa Cruz and southern California, they are targeted by ranchers, resulting in political tension about their conservation. In fact, cougars have been protected since 1990. However, 98 pumas are killed each year due to depredation hunting permits. It appears necessary to ensure coexistence between urban development, human activities, puma populations and their prey. In a recent study, development strategies are suggested, such as rural residence development, to ensure landscape connectivity and conservation of parcels where pumas have been geo-located. Nowadays, no cities are expanding regarding puma, deer or other wild animals’ living areas (to our modest knowledge!). The only measures taken when pumas are too close to urban zones consist in doing nothing or frightening or relocating it, and in the worst case killing it. And if designing our lives and activities regarding nature and wildlife was the challenge of tomorrow, would you be ready?


      Ideal residential development maintaining pumas landscape connectivity. Graphical abstract of the paper of Smith and al 2019

      Cited study: Wang, Y., Smith, J.A., Wilmers, C.C. (2017) Residential development alters behavior, movement, and energetics in an apex predator, the puma. PLoS ONE 12(10): e0184687. https://doi.org/10.1371/journal.pone.0184687

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    • Can new ecosystems develop in metal contaminated soils?by Robin Brouat and Théo Garcia

      Published by Charlotte Recapet the December 2, 2019 on 1:38 PM

      A recent study revealed that gray birch has interesting characteristics in ecological restoration, which allow the tree to support high metal contaminated soils.

      What is the experiment?

      Whereas the majority of scientists were kept in their laboratory testing contaminant, a group of American biologists performed an experiment in the field, a full-scale exercise.  In Jersey City, they measured a lot of photosynthetic parameters, in gray birch (Betulia populifolia) in two different conditions in Liberty State Park: One with High trace Metal Loads (HML) and the second with Low trace Metal Loads (LML). It results that none measured biophysical parameters vary. The only parameter that varied significantly was the leaf mass per area which decreased when the tree was in contaminated soil. This result can have two main explications. The first is that photosynthesis will no longer be affiliated with leaves but with other organs such as roots. The second is the fact that the tree will renew its leaves more often and this will impact its growth rate.


      Photo by Charlie Hohn

      Photograph by Richtid

      What is the link with ecological restoration?

      Gray birch can capture trace metals through their leaves and roots. This allows partial decontamination of areas polluted by heavy metals. Nevertheless, it is necessary to seed the plots after contamination so that only trees with a genotype with a high tolerance for trace metal concentrations grow. However, this decontamination by trees will not be possible anywhere in the world because trees are less efficient to get trace metals pollution in areas of high temperature and drought.

      It’s wonderful, but where is the new ecosystem promised?

      Yes, we are coming here. We can see an ecosystem like a pyramid with at its base the plants (also called primary producer) which convert the solar energy in organic matter for the higher steps of the trophic chain. In the study, the scientists explain that the diminution of leaf mass per area in HML affects the energy in entrance to the ecosystem. If less energy enters in the ecosystem, the whole ecosystem will be affected.

      Pretty cool! So what species could we find here?

      In theory this will be happened. But in practice, it could be quite different. Indeed, the diminution of Leaf Mass per Area is significantly, but does it could have a really impact on the ecosystem? The diminution it’s approximately 10g.m-2 and it’s not very well documented in the paper how this diminution could have an impact. In addition, we have just information about one species of primary producer; in a temperate forest we can found several tens of species which can do photosynthesis housing an animal diversity. For having a better idea of what kind of forestall ecosystem we can obtain, it seems better study the whole vegetal community of the site, and not simply a unique species.

      Hum, so this forest is not different than another one… So bad…

      Nevertheless, this study is interesting, and allows us to see the adaptation capacity of a specific tree to contaminated conditions. The gray birch is commonly used in ecological restoration, and the study proves that the species is robust for this type of projects. In the future, it will be frequent to walk in a forest, in a place in which in the past there was an industrial zone, without realizing the past of this forest. When local people will tell you that, before, there were factories. You will see the forest with a different way. And for this it will be a different forest for you. And it’s the more important.

      Cited study: Salisbury, A.B., Gallagher, F.J., Caplan, J.S., and Grabosky, J.C. (2018) Maintenance of photosynthesis by Betula populifolia in metal contaminated soils, Science of The Total Environment 625,1615-1627, https://doi.org/10.1016/j.scitotenv.2017.12.279.

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    • Pesticides and the power of earthwormsby Orane Becheler

      Published by Charlotte Recapet the May 10, 2019 on 6:04 PM

      We know that our current high use of some pesticides is harmful for the environment. For example, the controversy begun several years ago (National Geographic News, 2013 and Actu Environnement, 2018), about the disappearance of bees and the use of pesticides. Many of us have heard about this. In this context, assessing a priori the impacts of pesticides on environment can be helpful. This is why, five UK scientists have developed a model to anticipate the impacts of pesticides on the physiology of one species of earthworm, Eisenia fetida (A.S.A. Johnston and al., 2014).

      Why is it important?

                    The impact of pesticides on the growth and the reproduction of earthworms can lead to a huge decrease of their density and maybe to their disappearance. However, these organisms are very important for the soil quality. They provide good aeration and mixing of soil (call bioturbation) making it easier to absorb and keep water. Moreover, they greatly contribute to the degradation of organic matter making it accessible to other organisms. Indeed, a study of Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA, 2010) shows that, in a month, 1.5kg of earthworms (approximately 7,500 worms) can consume 30 days’ worth of a two-person household. In this way, plants growth better on a soil with earthworms than one without. This can be a great axis of reflexion about our way to produce vegetables. So, simulated impact of a pesticides on an area before destroy its ecosystem is a really good thing. Furthermore, we can see the importance of earthworms through their utilisation to evaluate the biodiversity in a participatory protocol (OPVT).

      In the video below, we can see the mix of soil by the earthworm’ displacements. Earthworms played a significant role in bioturbation.

      How did they do it?

                    These five UK scientists built complex model, call an energy-budget driven ABM. It consists of an interlocking of two model types: a huge one, an ABM (Agent Based Model), which contain many simple energy budget models. The first one allows to model how the population will progress, in other words the population’s dynamic. The second type allows to model life cycle processes for each earthworm from specified local conditions. Maybe the following picture can help you to understand.

      What did they found?

                    The main results are a decrease of growth and reproduction for the use of two pesticides.


      Modelling dose-response curves of two pesticides on the growth and the reproduction of Eisenia fetida. Adapted from the article.

                   Pesticides tested in this study are copper oxychloride and chlorpyrifos. The first one is widely used as fungicide and repellent, is not biodegradable and is “toxic to mammals and most biodiversity” (IUPAC, 2018). The second one is a current insecticide, “moderately persistent in soil systems, […] is highly toxic to mammals, […] birds, fish[es], aquatic invertebrates and honey bees” and “is classified as a reproduction toxicant, an acetyl cholinesterase inhibitor and a neurotoxicant” (IUPAC, 2018). So, the use of these pesticides can have large consequences not only on earthworms’ populations and so modelling consequences on others species is great.

                    Another study, presented by the Institut National de la Recherche Agronomique (INRA, 2014), shows also a decrease of earthworm populations when the quantity of used pesticides increases and vice versa (Pelosi C. et al., 2013).

      They have input local conditions of experimental data from literature. Their outputs fit great with the literature’s results, for non-toxic environments and for toxic ones, both individual life cycle processes and population dynamics.

      What is good and what is not?

                    Their model seems extremely complete because they incorporate varying food availability, use three steps of life with different parameters, for the adult stage they consider each step of processes under different feeding conditions and they consider interactions between individuals.

      In the ABM, they use a model landscape of 0.01 m2 patches of soil. It’s 10 cm2. I find this very small for a model which would simulate what it’s happening in the field. Moreover, further work is required to apply this approach to others species, maybe more ecologically relevant, and to implement the “heterogeneous distribution of chemicals in the soil and their degradation with time”. But this model can be useful to help to extrapolate data from laboratory to field or from species to species.

      Cited study: A.S.A. Johnston, M.E. Hodson, P. Thorbek and al. (2014) An energy budget agent-based model of earthworm populations and its application to study the effects of pesticides. Ecological Modelling 280, 5-17.

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    • Are vulture restaurants needed to sustain the densest breeding population of the African white-backed vulture?by Mikel Cherbero and Tom Laffleur

      Published by Charlotte Recapet the August 3, 2018 on 10:00 AM

      As obligate scavengers, vultures are entirely dependent on carrion. These last decades, carrion abundance has decreased in many areas. The two main causes of this trend are clearly identified. Natural habitat destruction reduces wild animal carrion abundance, which is the natural resource of scavengers. At the same time, the modification of agricultural practices, essentially the generalization of carcass rendering, has reduced the availability of cattle carrion. These factors have led to a negative trend on scavenger populations. This is especially the case in Africa, where most of avian scavenger species are now endangered. African savanna ecosystems were originally rich in avian scavengers, but most of the species are actually endangered.


      White-backed vultures feeding on zebra carrion - Bernard Dupont - CC BY-SA 2.0

      In this study, authors model the carrion ecology of an ecosystem in Swaziland which is home to the densest breeding population of the African white-backed vulture (Gyps africanus), a critically endangered species. They also study other threatened scavenger species of Swaziland: white-headed vulture (Trigonoceps occipitalis), Nubian vulture (Torgos tracheliotos), marabou stork (Leptoptilos crumenifer), tawny eagle (Aquila rapax) and bateleur (Terathopius ecaudatus). The purpose of this work is to better understand the feeding activity of the white backed vulture and to modelize population trends for these six species (using life-history traits and modelization of carrion availability), and based on these results authors discuss if the establishment of vulture restaurants would be beneficious.

      They first calculated the foraging radius (r) of the white-backed vulture, based on the Foraging radius concept theory. The foraging radius represents the radial distance from the nest in which the energy inputs are greater than the costs of feeding and needs of the vulture and its litter. This theory is adapted to this species, because vulture always comes back to the nest after feeding. They compiled available bibliography and collected data on metabolism and life-history parameters of the species. Using this data, they applied a model created with the same purpose by Ruxton & Houston in 2002 for the Ruppell’s vulture (Gyps rueppellii), which is phylogenetically and ecologically close to the white backed vulture.

      The results shows that the foraging radius is 260 km in the main part of the year. This radius is large, vultures can feed in neighboring countries (South Africa, Mozambique), it implies an international cooperation in the management of these endangered populations. A positive aspect is that individuals can spread over large area, so the studied population can form or sustain other populations. On the other hand this radius is much greater than the natural reserve surface, thus vultures can be exposed to several risks, like poisoning, when they are feeding. When vulture have to feed a chick, energy needs are logically greater so the foraging radius is reduced to 40 km. Carrion availability is more problematic during this period, which should therefore be targeted if vulture restaurants are setted up.

      Using novel Population Dynamics P-Systems, they show that carrion provided by wild ungulates biomass is currently enough to sustain this vulture species. According to the model, white-backed vulture population will continue increasing in Swaziland, and will pass from approximately 300 pairs to more than 500 in twenty years. The other studied avian scavenger populations will follow the same trend, but are far less abundant than white-backed vulture. The model shows also that three main species are composing vultures’ food: the Impala (Aepyceros melampus), the blue wildebeest (Connochaetes taurinus) and the plains zebra (Equus burchelli) represent 55 % of total carrion.

      However, in light of the forecasted population increases, food will become a limiting factor. This is particularly true for the period from November to April, for which the model show a carrion deficit. During this period African vultures are not breeding so they can go far away to feed themselves. But the model also shows a carrion deficit during the breeding season after five to thirteen years of simulation. This lack of food resources can be considered as a natural limiting factor. According to the model, the area has probably reach its maximum carrying capacity after twenty years.

      To conclude, authors suggest that setting up supplementary feeding stations in Swaziland should be seriously considered, especially during the breeding season. Good managed restaurants would have several advantages : secure the viability of the population and thus increase its capacity to act as a source population, avoid poisoning risks and create the opportunity to capture and tag vultures. This last point would allow to improve knowledge about the avian scavenger species, necessary for a more effective conservatory management.

      Cited study: Kane A., Jackson A.L., Monadjem A., Colomer M. A., Margalida A., 2015. Carrion ecology modelling for vulture conservation : are vulture restaurants needed to sustain the densest breeding population of the African white-backed vulture? Animal Conservation (18) 279-286.

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