Ascientist makes primers specific to a particular str fragment these primers are then used to amplify the str fragments from 10 different elephants would you expect the fragments to be the same size in all the elephants

The STR fragments will have different size for different animals.

Explanation:

STR means Short Tandem Repeats.STR forms the genome's microsatellite region.STR or microsatellite is that region of the genome where, about two to seven base pairs of the DNA (for example, ATGATGATGATG), are  repeated for multiple time. Such sequences can have few hundred repeats.While replicating these micro-satellite regions, the accuracy of the DNA polymerase in proof-reading the sequence of the newly synthesised strand, decreases, due to the multiple repeats.As a result of this, the DNA polymerase either adds more or adds less of such repeated sequences as compared to the parental DNA sequence. This results in generation of polymorphism (different microsatellite size in different individuals) in the repeat regions.Due to difference in size of the STR in different individuals, the size of the fragment amplified through PCR will vary for different elephants.