Yep, much clearer how you’ve written it out. If they wanted to keep it as a run-on sentence
“94 cats were fitted with rainbow sweaters in a test which resulted in a two-thirds reduction in the number of dead birds brought home, with no noted reduction in dead mice brought home, this is believed to be because birds can see the rainbow colours while the mice cannot.”
Much longer though when written with the signposting relational additions.
+ 
Yep, much clearer how you’ve written it out. If they wanted to keep it as a run-on sentence
“94 cats were fitted with rainbow sweaters in a test which resulted in a two-thirds reduction in the number of dead birds brought home, with no noted reduction in dead mice brought home, this is believed to be because birds can see the rainbow colours while the mice cannot.”
Much longer though when written with the signposting relational additions.