Time spent resting 
Average time each African elephants spent resting per night (± SD) in condition A presented in minutes. 

Resting position
All three African elephants engaged in both lying and standing rest on the concrete flooring and all three spent most time of resting in a lying position. The longest bout of standing rest observed for the African bull calf was one hour long and the older african elephants were observed engaging in standing rest for bouts longer than an hour. 

Non-lying rest *
Only the oldest of the African elephants (the mother of the two others) had one night of non-lying rest. 

Time spent resting 
Average time each Asian elephant spent resting per night (± SD) under the two conditions they were kept presented in minutes. 

Resting position
All individuals were observed engaging in standing and lying rest. However, the longest bout the Asian elephant calf was observed engaging in standing rest was only 7 minutes long whereas the older elephants could rest much longer in a standing position.
The bull and the younger females only engaged in lying rest on sand whereas the calf and the older female engaged in lying rest on both sand and concrete. The females started to engage in lying rest first after they gained access to sand.

Non-lying rest *
All three females exhibited nights of non-lying rest. As they did not engage in lying rest before they gained access to sand, they had many nights of non-lying rest. After the females gained access to sand two of them (the older and one of the younger) had some nights when they did not engage in lying rest. 

Time spent resting 
Both the time the African elephants were found to spend resting per night and the time the Asian elephants were found to spend resting per night found in the present study is in accordance with the findings of previous studies. The Asian elephants resting significantly more than the African elephants is also on accordance with the results of previous studies. Why the two species differ in how much they rest may be due to the two species having evolved in different environments. African elephants may have adapted to a higher predation pressure as they are exposed and as resting is a more vulnerable state than being awake they may have adapted to spend little time resting. This may also explain why the African elephant calf rested in a standing position for bouts up to an hour whereas the Asian elephant calf only were observed resting in a standing position for only 7 minutes.
The African elephants resting less could also be due to a trade-off between time spent feeding and time spent resting. African elephants being larger and may have to spend more time searching for food leaving them with less time to rest.  

All Asian elephants increased their time spent resting with the change in housing conditions with some individuals increasing their average time spent resting per night for up to an hour suggesting that some individuals may have experienced sleep deprivation and were catching up on their sleep when the conditions changed and might have been more comfortable.

Resting position 
Unlike the African elephants who all engaged in lying rest on concrete, most of the Asian elephants did not engage in lying rest on concrete which is in accordance with previous studies. This suggests that the resting behaviour of the two species is affected differently by the conditions they are housed in.  However, the older Asian elephant female and the Asian elephant calf did engage in lying rest on concrete. The older female likely engaged in lying rest on concrete as she had a preference for a certain area to rest and that area had concrete flooring throughout the study. For the calf it is most likely due to him wanting to rest close to the bull and sometimes the bull would stand on the concrete flooring, searching for food or so, meaning that the calf would have to lay down on concrete to be close to someone.
 

Non-lying rest
Elephants exhibiting nights of non-lying rest have been observed in previous studies with some individuals not engaging in lying rest every night. Previous studies have suggested that non-lying rest can be due to health issues such as arthritis, however this is not very likely the case of the African elephant female and the younger Asian elephants in the present study as they laid down to rest most nights.
It has been suggested that wild elephants exhibit nights of non-lying rest or not rest at all if there are disturbances. A previous study of elephants resting behaviour have suggested that non-lying rest among elephants can be seen as an adaptive behaviour of vigilance, but they also suggested that it could be seen as a abnormal behaviour due to the zoo setting. In my opinion, non-lying rest is an adaptive behaviour exhibited due to unnatural disturbances caused by the zoo setting.

*Non- lying rest refers to nights when an individual did not engage in lying rest at any time of the night.