Building table from list using nearest value?

Assumptions:

• data is always formatted as presented and there is always a complete 3-tuple of name/age/species
• first field of each line is spelled/capitalized exactly as in the example (the solution is based on an exact match)

Sample data file:

$ cat species.dat
1ID:42
2ID:85853
Name:Chris
Age:99
Species:Monkey
Name:Bob
Age:23
Species:Fish
Name:Alex
Age:67
Species:Cat
1ID:987
2ID:775437
Name:Tiffany
Age:32
Species:Dog
1ID:777
2ID:65336
Name:Becky
Age:122
Species:Hippo

One awk solution:

awk -F":" '
$1 == "1ID"     { id1=$2  ; next }
$1 == "2ID"     { id2=$2  ; next }
$1 == "Name"    { name=$2 ; next }
$1 == "Age"     { age=$2  ; next }
$1 == "Species" { print name,age,$2,id1,id2 }
' species.dat

NOTE: The next clauses are optional since each line is matching on a specific value in field 1 ($1).

Running the above generates:

Chris 99 Monkey 42 85853
Bob 23 Fish 42 85853
Alex 67 Cat 42 85853
Tiffany 32 Dog 987 775437
Becky 122 Hippo 777 65336