News

SE@K Thursday lunches – Summer 2023

For the last term of the 22/23 academic year, we have an exciting plan for SE@K and guest talks

  • 11th of May      Session : eDNA – Alex/Eleni; Cake : Eleni
  • 18th of May     Session : Occupancy data – Ardian Ardiantiono; Cake : James
  • 25th of May     Session : BeeWalk modelling – Fabian; Cake : Fabian
  • 1st of June       Session : Elephant killings – Kennedy Leneuiyia; Cake : Milly
  • 8th of June      Session : Extinction Models – Dave Roberts; Cake : Bruno
  • 15th of June     Session : Binary time series – Takis (TBC); Cake : Daniel
  • 22nd of June    Session : PhD student NCSE presentations; Cake : Diana
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grants, News

Bruno and Eleni visited Stockholm

The visit was part of their Swedish research council funded project on modelling overcoverage in population registers, in collaboration with Dr Eleonora Mussino.

The first paper from this project is already under review, using multiple systems estimation to estimate the number of immigrants who are present but have not been observed in any register each year.

They are currently developing capture-recapture-recovery models with temporary emigration as an alternative approach for estimating the probability that an individual is there given that they weren’t observed.

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News, Papers

New Biometrics paper

A new modelling framework for fast Bayesian inference in large occupancy data sets by Alex, Emily, Eleni and Byron just published in Biometrics.

The model accounts for spatio-temporal autocorrelation and gives robust inference on species presence, as evidence by the simulation results in the paper and the two case studies on one common and widespread and one rare species, using records from the Butterflies for the New Millennium database, producing occupancy indices spanning 45 years.

 

 

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Uncategorized

Spring term 2023 SE@K Thursday lunches

Spring term starts with the second half of Python training by Lena :-). Plan for the term in terms of sessions (and cake) below!

  1.  19th of January     Session : Python training II – Lena; Cake : Lena & Daniel
  2.  26th of January     Session : Daniel’s grant; Cake : Diana
  3.  2nd of February    Session : HMM paper – Diana; Cake : Eleni
  4.  9th of February     Session : HMM paper – Daniel; Cake : Oscar
  5.  16th of February   Session : HMM paper – Takis (guest lecture); Cake : Alex
  6.  23rd of February  Session : Variable selection/Hypothesis testing – Alex; Cake : James
  7.  2nd of March        Session : HMM – Fred (guest lecture); Cake : Fabian
  8.  9th of March         Session : Parameter redundancy – Daniel’s take; Cake : Tommy
  9. 16th of March         Session Swedish register data – Bruno&Eleni ; Cake : Milly
  10. 23th of March         Session : Swedish register data – Bruno&Eleni; Cake : Daniel
  11.  30th of March        Session : Spatio-temporal models – Oscar; Cake : Diana
  12.  6th of April             Session : eDNA data – Alex; Cake :  Eleni
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Uncategorized

Se@k weekly lunches

The SE@K group are meeting weekly for research lunch and socialising 🙂

Autumn term

First week was about introductions and a tasty lunch at Dolce Vita!

Second week was about staff talking about their research interests, with Diana talking to the group about parameter redundancy.

Third, fourth & fifth week were about research students talking about their research, with Tommy using randomised response techniques to estimate the proportion of people in the group who like/liked their supervisor (!), Milly talking about distance sampling, Ioannis talking about Bayesian non-parametrics and ABC and Lena talking about predator-prey models!

The term went on with learning about Gaussian processes from Alex, about PDEs from Eduard and about Python from Lena!

 

 

 

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News, Papers, Publications

New paper in Environmetrics by Alex

A vector of point processes for modeling interactions between and within species using capture-recapture data

Alex Diana, Eleni Matechou, Jim E. Griffin, Yadvendradev Jhala, Qamar Qureshi

Abstract

Capture-recapture (CR) data and corresponding models have been used extensively to estimate the size of wildlife populations when detection probability is less than 1. When the locations of traps or cameras used to capture or detect individuals are known, spatially-explicit CR models are used to infer the spatial pattern of the individual locations and population density. Individual locations, referred to as activity centers (ACs), are defined as the locations around which the individuals move. These ACs are typically assumed to be independent, and their spatial pattern is modeled using homogeneous Poisson processes. However, this assumption is often unrealistic, since individuals can interact with each other, either within a species or between different species. In this article, we consider a vector of point processes from the general class of interaction point processes and develop a model for CR data that can account for interactions, in particular repulsions, between and within multiple species. Interaction point processes present a challenge from an inferential perspective because of the intractability of the normalizing constant of the likelihood function, and hence standard Markov chain Monte Carlo procedures to perform Bayesian inference cannot be applied. Therefore, we adopt an inference procedure based on the Monte Carlo Metropolis Hastings algorithm, which scales well when modeling more than one species. Finally, we adopt an inference method for jointly sampling the latent ACs and the population size based on birth and death processes. This approach also allows us to adaptively tune the proposal distribution of new points, which leads to better mixing especially in the case of non-uniformly distributed traps. We apply the model to a CR data-set on leopards and tigers collected at the Corbett Tiger Reserve in India. Our findings suggest that between species repulsion is stronger than within species, while tiger population density is higher than leopard population density at the park.

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