Complex sentence: This occurs because after copulation, males lose up to 11% of their body mass so they need to take time to sequester resources in order to deliver a spermatophore to the next female they mate with.
Split into simpler sentences: This occurs because males lose up to 11% of their body mass during mating. Once they are done mating, they need time to sequester resources that will allow them to deliver a spermatophore to the next female they mate with.