Speculative Reproductive and Social Behavior in Tyrannosaurids (speculation)

[Sim Koning <simkoning@msn.com>]

 Some interesting things come to mind when you consider both the estimated 
life span and the possibility of pack hunting in tyrannosaurs. The life span 
of tyrannosaurids is estimated to be between 25 to 30 years years, with 
sexual maturity being reached possibly within the 4 year rapid growth period 
(12 to 16). This would mean that the young would reach sexual maturity at 
about the same time their parents die of old age. With this in mind, 
consider this (highly) hypothetical scenario based on the multiple 
Albertosaur specimens found together and described by Currie et al.

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-Note- This is purely a fun intellectual exorcise on my part and an attempt 
to logically sort out one possible scenario for pack hunting tyrannosaurids. 
I also gave them names so this would be less confusing to the reader.

 We have 10 Albertosaurs in a pack; 2 of them represent fully grown 
sexually mature sisters, both 21 years old, we will call them Sue and Jane. 
There is also an unrelated 17 year old alpha male which mates with the 2 
females, we will call him Stan. There are 4 sub adults just reaching puberty 
from a younger clutch related to Sue and Jane, each of them are about 13 
years of age; they consist of 3 males and 1 female. The 3 sub adult males 
are Phil, Bob and John, the female is Lisa. The sub adults assist Jane, Sue 
and Stan in hunting and with the care of their young, much like some birds 
of prey do today. Lastly there is a small 10 year old male named Tinker and 
two 2 year old males named Mike and Ike, the last 2 are the only surviving 
offspring of Sue and Jane.

Unrelated male
Stan 17

Siblings or Cousins
Sue 21
Jane 21
Phil 13
Bob 13
John 13
Lisa 13
Tinker 10

Only surviving offspring of Sue and Jane
Mike & Ike 2


 3 years pass, Sue and Jane die. Sue dies in a territorial dispute with a 
Daspletosaurus and Jane is killed from a disastrous trip and fall while 
chasing a hadrosaur, they have 6 more offspring before they die. Tinker, now 
13, fills the sub adult role in the pack. Phil, Bob and John are now adults 
at 16 years of age; they leave to find their own mates while Stan mates with 
Lisa, they have 8 offspring together. Mike and Ike are now 5.

 4 more years pass and the aging 24 year old Stan is killed by a healthier 
19 year old named Thomas. Thomas mates with the now 20 year old Lisa and 
drives away Tinker who moves on to find his own mate. Lisa is able to 
protect her dead sisters' offspring, as well as her own, from Thomas with 
her larger size and greater strength. 3 of her sisters' 6 offspring have 
died and the rest are now 6 years old, 4 of her own young have died and the 
rest are now 4. Mike is eaten by a crocodile and Ike is now 9.

7 years pass, Lisa and Stan die and Ike is now 16 and almost fully grown. 
Mike is left with his siblings and cousins, 3 of which are 13, 4 are 11 and 
several more are under 10. Mike leaves to find a mate and is replaced by an 
18 year old unrelated male, which mates with 2 of the young 13 year old 
females while he kills or drives away the males. A few of the orphaned young 
males manage to survive into adulthood by banding together in a bachelor 
pack while using their greater speed and maneuverability to catch prey too 
fast for the adults. The cycle continues?.
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 Now you?ll have to forgive me if I made a mistake somewhere in there, but 
the point was to illustrate the fact that adult tyrannosaurids would have a 
rather limited time to breed and raise their young to adulthood. In fact 
they would hardly have time to see their first clutch reach maturity. This 
would seem to be good motivation for parental care, as well as sibling care. 
Once the oldest members of the pack die, pack leading duties might have been 
taken over by the younger females, while the males left in search of 
unrelated packs.

Again, I know this is all pure speculation on my part.  Let me know if any 
of you have any ideas on how a parental care and pack behavior might work 
with their relatively short adult life spans in consideration.

Simeon Koning

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