To cite the 'trajr' package in publications use:

McLean, D. J., & Skowron Volponi, M. A. (2018). trajr: An R package for characterisation of animal trajectories. Ethology, 124(6), 440-448. https://doi.org/10.1111/eth.12739

Corresponding BibTeX entry:

  @Article{doi:10.1111/eth.12739,
    title = {trajr: An R package for characterisation of animal
      trajectories},
    author = {Donald James McLean and Marta A. Skowron Volponi},
    year = {2018},
    journal = {Ethology},
    volume = {124},
    number = {6},
    doi = {10.1111/eth.12739},
    url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/eth.12739},
  }