While the results were likely to be distressing for both the tree-kangaroos and the researcher, this provided a unique opportunity to observe how 
(the results; were; likely to be distressing for both the tree-kangaroos and the researcher) (the results; to be distressing; for both the tree-kangaroos and the researcher) (this; provided; a unique opportunity to observe how)
the results the results this
were to be distressing provided
likely to be distressing for both the tree-kangaroos and the researcher
for both the tree-kangaroos and the researcher
a unique opportunity to observe how