Tatu and Loulis lived at the Chimpanzee & Human Communication Institute in Ellensburg Washington from 1980 until they moved to Fauna Foundation in August 2013. Tatu had acquired signs of American Sign Language (ASL) during her childhood from humans, and Loulis from other signing chimpanzees. All caregivers at CHCI interacted with Tatu, Loulis and the other signing chimpanzees in their family using ASL (Fouts & Mills, 1997). Caregivers recorded all signs they observed in a daily Sign Checklists. When Tatu and Loulis moved to Fauna a few of the caregivers from CHCI accompanied them, and the caregivers continued to record the signs in daily Sign Checklists. Dombrausky, Hings, Jensvold and Shaw presented a comparison of the variety of signs from CHCI days to Fauna days at a recent psychological conference and this post highlights some of these findings. (Dombruasky, et al. 2017).

We selected Sign Checklists from 2004-2006 (CHCI) and 2014-2016 (Fauna Foundation). We compared the variety of vocabulary items between these periods that each chimpanzee used in a day, rather than the volume of signing.
Table 1, below, shows the range of the number of different signs that appeared in a day. For Tatu the range at CHCI was 1 – 42 versus 1- 58 at Fauna. At each location she had at least one day when only one sign was recorded. At Fauna she had at least one day when 58 different signs were recorded. Loulis’ range was the same at each location 1-12. This shows they are still using a large breadth of vocabulary despite the change in environment.

We also compared the frequency of each vocabulary item. The top five signs appear in Table 2. Loulis’ top sign was always CHASE a favored activity. At CHCI Tatu’s top signs involved activities. SMELL was frequent which is a game involving smelling the breath of a friend. MASK was frequent and was a game in which a friend dons a mask. At Fauna in the first two years Tatu’s top sign shifted to food items such as MILK and CHEESE.

Table 2. Top five signs for each chimpanzee by year.

At Fauna both chimpanzees used indexical signs more often in the third year, THAT for example. Indexical signs, which use pointing, are intelligible by signers and nonsigners alike. At Fauna there are caregivers who do not sign. Tatu and Loulis adjusted their signing to the caregivers’ comprehension. This is a theme prevalent in the sign language studies at Fauna Foundation. The chimpanzees adjust appropriately to the state of their conversational partner. (see Bodamer & Gardner, 2002; Jensvold & Gardner, 2000; Leitten et al, 2012).

We are grateful to the years of support from Winley Foundation, David Bohnett Foundation, and Friends of Washoe for supporting caregivers who are skilled in American Sign Language and are reliable data collectors.
For the complete poster please visit https://osf.io/dngz6/

References Sited

Bodamar, M. D., & Gardner, R. A. (2002). How cross-fostered chimpanzees (Pan troglodytes) initiate and maintain conversations. Journal of Comparative Psychology, 116, 12.
Dombrausky, K., Hings, C., Jensvold, M.L., & Shaw, H. (2017, April). Variability in Sign Use in Chimpanzees Before and After Relocation. Poster Presented at Rocky Mountain Psychological Association, Salt Lake City, UT.
Fouts, R., & Mills, S. T. (1997). Next of kin: What chimpanzees have taught me about who we are.
Jensvold, M.L.A., & Gardner, R.A. (2000). Interactive use of sign language by cross-fostered chimpanzees. Journal of Comparative Psychology, 114, 335-346.
Leitten, L., Jensvold, M.L., Fouts, R., & Wallin, J. (2012). Contingency in requests of signing chimpanzees (Pan troglodytes). Interaction Studies, 13, 147-164.
Photo: Tatu signs BLACK,  © NJ Wight