[R] Merging two data sets

[Kurt_Helf at nps.gov]

Greetings
    I need to merge two data sets.  The first data set contains information
on individual organisms roosting in clusters,e.g., cluster one has 5
individuals: 3 females, two males, and one juvenile and so on for hundreds
of clusters.  The second data set contains temperature data on each of the
plots from the first data set.  The problem: the second data set only has
one data point per cluster and I need to match or duplicate those
temperature data with each individual organism in each cluster from the
first data set.  I hope this explanation is clear.  How do I go about doing
this?  Thanks in advance.
Cheers
Kurt