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Mouse Project at Silwood Park

Summary

We study populations of wood mice, yellow-collared mice and bank voles in native deciduous woodlands at Silwood Park, Ascot, UK. The general goal is to gain a better understanding of the individual and population level drivers of rodent population dynamics accounting for interspecific interactions and weather drivers. At the individual level we collect physiological, morphological, behavioural and life history data, and at the population level we monitor weather, food availability and microhabitat features in a spatially-explicit context. This is possible thanks to a novel system of mobile data loggers and a high resolution mapping of the study area. We also use the wealth of data collected from this system to parameterize population models and test specific hypotheses by perturbing demographic functions and assessing the sensitivity of population growth to different parameters. These empirical studies are allowing us to develop more ambitious theory inclusive of the sorts of complex interactions that we see in natural populations. More than 20 master, PhD and undergraduate students have worked in these systems. We are also developing rodent wireless tracking technologies in collaboration with the department of electronic engineering at Imperial College London, that may lead to real time monitoring of rodents. 

This project has been continuously collecting data on wild rodents since July 2008. It led to the installation of a monitoring facility endowed with electricity and internet in the middle of a natural woodland in England. This has led to unmatched opportunities to collect high quality data to conduct ground-breaking research in rodent population ecology, evolutionary ecology and community dynamics. 



What were the motivations to start this project ? 

I am motivated by the idea of conducting research that leads to a more predictive ecological science. A science that will allow us to understand and manage the biosphere intelligently. By providing a comprehensive understanding of the interplay of different actors in natural scenarios, it will ultimately allow us to make predictions into the future about the dynamics of relatively complex systems. However, this type of science requires effort to harness the complexity that is relevant to particular study systems. 

To achieve this goal, we must understand the effects of trait value on life histories, as well as how these effects vary in different environmental and species community contexts, i.e. what are the trait by trait, and trait by environment interactions on demography. Both require a detailed research program that considers measuring temporally and spatially-explicit ecological and evolutionary quantities. I aimed at  generating the first long-term individual-based project of his kind. This type of research should allow us to advance faster in our aim to understand the drivers of population and ecological dynamics. The mouse project at Silwood Park aimed to fill an important gap in the fields of ecology and evolution: to understand the drivers of population dynamics of species with fast life histories. 

How was the project born ?

The Mouse project is the brainchild of Dr Aurelio F. Malo, who conceived this project in early 2007 whilst on a Fulbright fellowship at the Smithsonian Institution, Washington DC. He wrote and was awarded a Marie Curie proposal to conduct his research at Imperial College London in 2008, when the project took off. Field work began in summer 2008. Soon after the project had 4 other students working on the project.

What is the main long-term goal of the mouse project ? 

Allow a better understanding of the drivers of population dynamics in natural populations. 

Why rodents ? 

There were no long-term individual based projects focusing on understanding species with fast life histories such as rodents, one of the most important groups of mammals: 

1) Rodents are the mammals with the highest abundance of species (40% of total mammal species). 

2) They represent a large proportion of the biomass available to higher tropic levels in terrestrial communities, such as aerial or terrestrial predators (some of them endangered).

3) Rodents also have an important role in disease spread, posing health risks to humans and other mammals as direct and indirect vectors of disease.

4) Finally, the fast reproductive rates of rodents makes many species potentially dangerous pests that can impact both natural ecosystems and rural human communities, with wide economic impacts as crop raiders.

Figure 1. Schematic diagram showing the different datasets generated and the number of records they hold.

To this end the data collection carefully considers:

  • 1) Individual level traits: Physiological, morphological, behavioural and life-history traits
  • 2) A spatially-explicit approach
  • 3) Population level variables such as density, age structure and sex ratio
  • 4) Environmental level variables impacting the population (temperature, weather, food abundance)
  • 5) Monitors other relevant species (competitors/parasites/predators)  in the community to account for multi-species interactions

Given that individual life trajectories are dependent on the environment individuals experience, I aimed at collecting high-resolution information on individual temporal-space use patterns (point 2 above). For this, I devised and constructed new rodent monitoring technology using PIT-tag readers (Mike Francis Ltd) and deployed this new technology in the field. 








Study site selection and location

The study site was selected after trapping in 13 different locations within Silwood Park grounds in July, August and September 2008. I selected the less perturbed trapping site area, with highest plant diversity and highest wood mouse abundances as the study site to set up the study site for this project. 

The study site is located in the mixed deciduous woodland of Nash’s Copse at the north end of Silwood Park, Imperial College London (OS grid ref.: SU 9430 6920). The study site contains an area of 2.47 ha, subdivided into 10 x 10 m grid squares. According to the National Vegetation Classification system, the study site is a Quercus robur – Pteridium aquilinum – Rubus fruticosus woodland (W10a Typical sub-community). The dominant tree species are two different birch species (Betula pendula and Betula pubescens), with some ancient beech trees (Fagus sylvatica), sycamore (Acer pseudoplanatus), oak (Quercus petraea), ash (Fraxinus excelsior) and alder (Alnus glutinosa). The shrub layer is dominated by rhododendron (Rhododendron ponticum) and hazel (Corylus avellana). Bamboo (Sasa palmate) is also present in a single patch. Ground layer species are bluebell (Hyacinthoides non-scripta), bracken (Pteridium aquilinum) and wood sorrel (Oxalis acetosella).

 


What are the main study species ?

Three rodent species occur in the study site:  wood mouse (Apodemus sylvaticus), yellow necked mouse and bank vole glareolus). The study focuses on the wood mouse population, a small rodent species which is widely distributed across Europe and common in the United Kingdom, inhabiting mainly woodland, but also grassland and cultivated fields. They are an important seed dispersal species for northern hemisphere temperate ecosystems. The wood mouse is the staple prey of aerial generalist predators such as Tawny owls and of other terrestrial predators like weasels and foxes present in the area. Other mammals such as rabbits, sika deer, muntjac, roe deer, and badgers have been seen in the study site.

What data do we collect ?

 

We collect individual and population-level data. Individual-level data includes detailed phenotypic data from rodents at capture, and behavioural measures. Ecological data includes food abundance, indirect measures of predation risk, weather data and the presence of competitor species.


Study site mapping

All habitat features in our study site at a 1m2 scale resolution. Trees and hazel (Corylus avellana) are tagged, their trunk measured, crown area estimated and their location recorded. The location and dimensions of fallen trees (here forth logs), stumps and woody debris are recorded and measured. All patches of cover-providing species such as Rhododendron (R. ponticum) and bamboo (S. palmate) are mapped The other dominant shrub species, C. avellana, is treated as a food-proving species as the sparse canopy does not provide cover in the same way that rhododendron and bamboo. Maps of the study site are created with GIS (ArcGIS, v9.3) with absolute and relative coverage of shrubs and ground layer plants, and tree radii for each square meter. In addition, log volume, stump volume, tree volume, and debris volume are generated for each square meter in the study site. The map is updated biweekly to include changes in habitat features, such as tree fall or extension of shrubs or ground cover plants.

Map of the study site at Imperial College London

Map of the study site at Nash's Copse (Silwood Park, Imperial College London). Total size 2.47 hectares. Grids are 100m2 (10x10m)


Zoom in of an area of the study site depicting in more detail the microhabitat structures and tree species mapped. Grids are 100m2 (10x10m).


Trapping sessions

Trapping sessions were conducted weekly for the first 2 years and fortnightly since. At each trapping session, one trap is placed in a selected 100m2 square in a wooden box to protect the trap and caught rodent from rain, temperature fluctuations, and other mammals. Food, a source of moisture and cottonwool  are provided in each trap. In front of each trap a small apple piece and one peanut are placed to lead mice into the trap. In addition, apple juice is sprayed next to the trap to increase catchment area. Traps are set up approximately 2 hours before sunset and collected the following day 2 hours before sunrise. All caught mice are weighed and sexed. Individuals (>15g) caught for the first time are tagged with a 12mm x 2mm RFID Passive Integrated Transponder (PIT) tag. Additionally, phenotypic and behavioural data is collected also collected. Each individual is released back at the location where it was caught.


Spatio-temporal use patterns

In 2009 Dr. Malo, conceived and designed a system to monitor spatial-temporal use patterns. Ten mobile data loggers randomly rotate across the study site, allowing habitat space use (at a 1m scale resolution) and temporal use (at a 1 second resolution) to be measured for each marked individual in the study site. The records are saved on a memory stick and the data are downloaded on a daily basis. Each logger is used within a specific 0.24ha area and was moved daily on a random base between different 100m2 squares within the specific area (n=7x/week). Within one square the data logger was placed at a random 1m2 coordinate. Once all squares within one 0.24ha area were used for one night, the list of squares was re-randomised. The minimum distance between two different data loggers and/or two subsequent squares for the same data loggers was 30m. Spatial location accuracy was ±1m.  The system uses mobile crates fitted with PIT data-loggers constructed by Francis Scientific Instruments Ltd. For more details e-mail Aurelio Malo at aureliomalo@gmail.com



Figure 2. Mobile data logger technology to monitor rodent space use. Idea and design by A.F. Malo. (i) Mobile data logger boxes randomly rotate daily between the study site grid squares to allow for random sampling of rodent space use behaviour. Grid resolution 10x10m (within a 100m2 grid, the specific 1m2 location is also randomized). The picture also shows a trap cover for grid Z10 in which a Sherman trap is placed on trapping nights. (ii) Inside view of a mobile data logger box. The mouse runs through the black pipe, the PIT tag is then detected by the grey loop antenna (around the plastic white T-junction) and recorded in a removable memory stick connected to the circuit board. The recorded data is downloaded daily into a laptop. (iii) Wooden box within each mobile data logger box. Mice can access this through the plastic white T-junction from outside the box. The nest box is filled with a small layer of sawdust and one peanut to entice mice into the boxes.



Infrared motion-activated cameras monitoring rodent foraging behaviour across the study site and streaming footage real-time into the internet. Idea AF Malo. Design by Marc Brouard (with input from Dennis Wildman and AF Malo). See video below.


Wood mouse seed foraging experiment using infra-red cameras



E
arly on, and in an attempt to better characterize spatio-temporal use patterns by mice, Dr Malo instigated collaborations with electronic engineers Prof Thanassis Manikas and Christos Pappavassiliou, interested in the localization problem is small bodied species (location at high spatio-temporal resolutions), antenna arrays and signal processing. Results on this front will be posted as progress is made.


Findings

  • An invasive wide-spread shrub in the UK (Rhododendron ponticum) has a positive effect on mouse density and aggregation. This happens because the thick cover provided by the evergreen shrub provides refuge aerial generalist predators such as Tawny owls. 
  • The fact that logs are positively associated with trapping success in the open woodland but not under rhododendron suggests no need for protective structures such as logs is required once the thick Rhododendron canopy is present.  
  • During the breeding season mice from both sexes compete for Rhododendron areas where to establish their territories, leading to an increased probability of finding mice in open areas of the woodland where predation risk is higher.  
  • Mouse survival is higher under Rhododendron areas, providing the demographic evidence required to confirm the above findings. This has been shown using multi-state capture-recapture models. 
  • Studies in natural populations need to account for the seasonality that matters to the species. For instance, we have shown that habitat  factors are important drivers of HR size during late breeding season, whilst individual-level factors are important drivers of HR during the early breeding season
  • Different processes operating at different spatial scales


 Publications

Colchero F, Jones OR, Conde DA1, Hodgson D, Zajitschek F, Schmidt BR, Malo AF, Alberts SC, Becker PH, Bouwhuis S, Bronikowski AM, De Vleeschouwer KM, Delahay RJ, Dummermuth S, Fernández-Duque E, Frisenvaenge J, Hesselsøe M, Larson S, Lemaître JF, McDonald J, Miller DAW, O'Donnell C, Packer C, Raboy BE, Reading CJ, Wapstra E, Weimerskirch H, While GM, Baudisch A, Flatt T, Coulson T, Gaillard JM. 2018. The diversity of population responses to environmental change. Ecology letters. doi: 10.1111/ele.13195.

Godsall B, Coulson T, Malo AF* 2014. From physiology to space use: energy reserves and androgenization explain home range size variation in Apodemus sylvaticus Journal of Animal Ecology. 83(1):126-35.

Malo AF*, Godsall B, Prebble C, Grange Z, McCandless S, Taylor A, Coulson T. 2013 . Positive effects of an invasive shrub on aggregation and abundance of a native small rodent. Behavioral Ecology, 24 (3):759-767.

Stratton et al., Getting the full picture on personality: Assessing within-individual, between-individual and between-population variation in behaviour in the wood mouse. Submitted to Animal Behaviour. 

Malo AF*, A Taylor. Rhododendron-driven asymmetric seed dispersal by rodents: A novel mechanism for refuge-mediated apparent competition. Submitted: Journal of Plant Ecology.

Hicks O, Godsall B, Coulson T, Malo AF* Reassessing dominance: testosterone and not body size predicts social interactions in a wild rodent population. In Revision.

 

PhD Projects (3)


Ben Godsall, 2015. Mechanisms of space use in the wood mouse, Apodemus sylvaticus. Imperial College London. 


Tim Stratton, 2015. Use of personality traits to improve reintroduction success: the effects of behavioural variation at release. Nottingham Trent University.


Severin Dressen, 2016. Population dynamics and space use in voles. University of Oxford.

 

MRes and MSc Research Projects (20)


20. Sean Keane. Msc. 2018-2019. 

19. Peter Stewart. MRes. 2018-2019. Individual-level factors and predation risk response.

18. Rachel Cates. Honours Thesis. 2015Moonlight effects on the wood mouse activity patterns. 

17. Bryony Allen. MRes. 2014. Associations within a mixed-species rodent community social network.

16. Barker,R. MSc. 2013 The effects of interspecific competition on Apodemus sylvaticus

15. McLoughlin, S. MSc. Ecological Applications. 2012 Personality trait effects on wood mice daily activity patterns

14. Moorehouse-Gann,RM. MSc. Ecol. Evol. Cons. 2012 Influence of invertebrate food resources in space use patterns and reproductive success: an experimental approach

13. Dreben, S. MSc. Ecol. Evol. Cons. 2012 At what scale do microhabitat structures influence mouse space use behaviour?

12. Sandbach, L. MRes.  2011-2012 Metabolic rate effects on rodent over-wintering survival

11. Hicks, O. MRes. 2011-2012 Phenotypic, ecological and environmental determinants of social interactions and its effects on wood mice over-winter survival

10. Brouard,M. MRes. 2011-2012 Seed predation and dispersal behaviour in Apodemus sylvaticus

9. Oxley, A. MSc. Environmental Technology. 2011 Assessing the impact of forest edges and matrix types on the composition of small mammals in the Interior Atlantic Forest of Paraguay

8. Powell, T.  Ecol. Evol. Cons. 2011. Spatial home-range determinants on a wood mouse population during winter

7. Kingcome, G. MRes. 2010-2011.Spatio-temporal seed crop variation effects on mouse space use and activity patterns

6. McCandless, S-J. MSc. Ecol. Evol. Cons. 2010 Determinants of female reproduction in the wood mouse, Apodemus sylvaticus

5. Wevill, C. MSc. Ecol. Evol. Cons. 2010 An integrated approach to identify individual determinants of space use

4. Grange, Z. MSc. Ecol. Evol. Cons. 2009 Determinants of parasite prevalence and intensity in Apodemus sylvaticus

3. Taylor, A. MSc. Cons. Forest. 2009 The influence of invasive species upon natural communities

2. Prebble, C. MSc.Ecol. Evol. Cons. 2009 Behavioural responses of Apodemus sylvaticus to direct and indirect predator cues.

1. Godsall, B. MRes. Ecol. Evol. Cons. 2009. The influence of predation risk and food abundance on space use by Apodemus sylvaticus.


Research Fellows

  • Dr Aurelio F. Malo (Marie Curie, ERC)


Media / Outreach

  • Our rodent research at Wytham woods (Oxford) featured at the Oxford's Natural History Museum, Oxford. 
    Impact and Outreach: A Laboratory with leaves


  • TV Interview to Dr Malo at BBC Breakfast TV program on the effects of the invasive species.

    • Interview to Dr Malo in BBC Nature website the effects of the invasive Rhododendron on wood mouse populations. 


    Acknowledgements

    Individuals

    Dr Ben Godsall for his invaluable work in the field, its intensity and his formidable attitude. Ben contributed as a 4x4 field technician as well through his work as the first part-time PhD student in the project mainly working mainly with genetics. Ben has also contributed widely to all the other components of the project in one way or another.

    Prof Tim Coulson, for welcoming my ideas, for his encouragement and for initially sponsoring my Marie Curie Fellowship at his lab. Without Tim's and Imperial's enthusiastic welcome the project would have not taken off. In 2013 a replicate of this study system was set up at Wytham woods (Oxford), precisely in the same woodlands where pioneering figure Charles Elton, who focused his research on small mammals and population cycles, allowed the modern science of ecology to take off. Silwood Park project continues to be run by Aurelio Malo, and Wytham woods project is run my Prof Tim Coulson. Both projects share methods and insights for mutual benefit. 

    Severin Dressen and Rose Mary Moorehouse-Gann helped intensely during the re-mapping of the study site and helped with the GIS phase of the work. Severin has continued his great work in the project until recently.

    Dr Sarah Knowles, came to collaborate in the project as an advanced postdoc and helped with the running the trapping sessions and other field work components from Sept 2014 to November 2015, to which Ben and Severin also strongly contributed.

    Prof Mick Crawleyas a colleague and Campus Dean, for constant support and for providing critical information about Rhododendron in the study site.

    Engineer Michael Francis (Michael Francis Ltd.) for his invaluable technical assistant with the the data-loggers and software issues.

    Technicians Igor Lisenko for GIS expertise and Paul Beasley from Imperial's hardware store.

    Colleagues Prof Simon Leather (for help with invertebrate research), Joe Smith (Panthera), Ben Godsall (help with artificial mouse burrows).

    Volunteers Anthony, Michael Massam, Lukas Lukoski, Helen Davies.


    Funding Sources: 

    • University of Alcalá endowment fund to Dr Aurelio Malo
    • Spanish Ministry of Science Innovation and Universities (Ramon y Cajal Fellowship to Dr Aurelio Malo)
    • European Research Council (ERC senior grant Prof Coulson. This proposal included Dr Malo's rodent study system as 1 of the 3 components of the research proposal)
    • NERC (Independent Research Fellowship to Dr Sarah Knowles)
    • European Research Council (Marie Curie Fellowship to Dr Aurelio Malo)
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