1. Putting the cart before the horse: claims for mirror self-recognition in horses are unfounded

   • Gordon G. Gallup Jr.
   • James R. Anderson

   Commentary 27 July 2021 Pages: 1 - 4

2. Quantitative abilities of invertebrates: a methodological review

   • Elia Gatto
   • Olli J. Loukola
   • Christian Agrillo

   Review Open access 19 July 2021 Pages: 5 - 19

   

3. Are you my mummy? Long-term olfactory memory of mother’s body odour by offspring in the domestic cat

   • Péter Szenczi
   • Andrea Urrutia
   • Oxána Bánszegi

   Short Communication 26 July 2021 Pages: 21 - 26

   

4. Quantity discrimination in a spontaneous task in a poison frog

   • Sunil Khatiwada
   • Sabrina S. Burmeister

   Short Communication 28 July 2021 Pages: 27 - 32

   

5. Visual snake aversion in Octodon degus and C57BL/6 mice

   • Shigeru Watanabe
   • Henning Scheich
   • Kazutaka Shinozuka

   Original Paper 22 June 2021 Pages: 33 - 41

   

6. Dogs (Canis lupus familiaris) are susceptible to the Kanizsa’s triangle illusion

   • Miina Lõoke
   • Lieta Marinelli
   • Paolo Mongillo

   Original Paper Open access 16 July 2021 Pages: 43 - 51

   

7. African elephants can detect water from natural and artificial sources via olfactory cues

   • Matthew Wood
   • Simon Chamaillé-Jammes
   • Adrian M. Shrader

   Original Paper 22 July 2021 Pages: 53 - 61

   

8. Habituation in anuran tadpoles and the role of risk uncertainty

   • Mariana Pueta
   • Dolores Ardanaz
   • Juan Cruz Tallone

   Original Paper 24 July 2021 Pages: 63 - 72

   

9. Positional inference in rhesus macaques

   • Greg Jensen
   • Vincent P. Ferrera
   • Herbert S. Terrace

   Original Paper 24 July 2021 Pages: 73 - 93

   

10. Domestic cats (Felis catus) prefer freely available food over food that requires effort

    • Mikel M. Delgado
    • Brandon Sang Gyu Han
    • Melissa J. Bain

    Original Paper Open access 26 July 2021 Pages: 95 - 102

    

11. Effects of early noise exposure on hippocampal-dependent behaviors during adolescence in male rats: influence of different housing conditions

    • Sonia Jazmín Molina
    • Ángel Emanuel Lietti
    • Laura Ruth Guelman

    Original Paper 28 July 2021 Pages: 103 - 120

    

12. Evaluating the accuracy of facial expressions as emotion indicators across contexts in dogs

    • A. Bremhorst
    • D. S. Mills
    • S. Riemer

    Original Paper Open access 02 August 2021 Pages: 121 - 136

    

13. Is this love? Sex differences in dog-owner attachment behavior suggest similarities with adult human bonds

    • Biagio D’Aniello
    • Anna Scandurra
    • Paolo Mongillo

    Original Paper Open access 05 August 2021 Pages: 137 - 148

    

14. All units are equal in humpback whale songs, but some are more equal than others

    • Eduardo Mercado III
    • Christina E. Perazio

    Original Paper 06 August 2021 Pages: 149 - 177

    

15. Group size, partner choice and collaborative actions in male Indo-Pacific bottlenose dolphins (Tursiops aduncus)

    • Eszter Matrai
    • Shaw Ting Kwok
    • Ákos Pogány

    Original Paper 07 August 2021 Pages: 179 - 193

    

16. The “right” side of sleeping: laterality in resting behaviour of Aldabra giant tortoises (Aldabrachelys gigantea)

    • Caterina Spiezio
    • Camillo Sandri
    • Barbara Regaiolli

    Original Paper Open access 09 August 2021 Pages: 195 - 203

    

17. How visual system configuration can play a role in individual recognition: a visual modeling study

    • Rebecca Trapp
    • Esteban Fernández-Juricic

    Original Paper 12 August 2021 Pages: 205 - 216

    

18. Who is there? Captive western gorillas distinguish human voices based on familiarity and nature of previous interactions

    • Roberta Salmi
    • Caroline E. Jones
    • Jodi Carrigan

    Original Paper 14 August 2021 Pages: 217 - 228

    

19. Correction to: How visual system configuration can play a role in individual recognition: a visual modeling study

    • Rebecca Trapp
    • Esteban Fernández-Juricic

    Correction 29 October 2021 Pages: 229 - 229