The ssh agent cannot 'resolve hostname' when called from within a bash script

Question

I have a bash script

#!/bin/bash scp -r some_directory remote_host:~ 

which I made executable with chmod u+x. The remote_host has been defined in my .ssh/config as follows:

Host remote_host HostName ec2-x-xxx-xx-xxx.eu-central-1.compute.amazonaws.com User ubuntu IdentityFile ~/path_to_pem_file/pem_file.pem IdentitiesOnly yes 

when I call scp -r some_directory remote_host:~ or ssh remote_host it works without problems to access the remote machine via ssh. However inside the bash script it doesn't work. I get the following error:

ssh: Could not resolve hostname mochacle: Name or service not known lost connection ssh: Could not resolve hostname mochacle: Name or service not known ssh: Could not resolve hostname mochacle: Name or service not known 

irrespective of whether I sudo the execution of the script or not.