Puppy or Adult Dog - What the Adoption Data Actually Shows

By Paw Multiverse Editorial Team · Updated August 4, 2026

This decision is usually made emotionally and then justified afterwards. There is enough published data to do it the other way round, and the data is more interesting than either side of the usual argument.

The study that should inform this decision

Powell, Reinhard, Satriale, Morris, Serpell and Watson published an analysis in Scientific Reports in 2021 covering 23,932 adopted animals, looking at who came back and why. The overall return rate was 9.2 per cent, but that hides a large species difference: 16.3 per cent of dogs were returned against 4.2 per cent of cats.

Age at adoption predicted return strongly. Adult dogs had the greatest odds of post adoption return, with an odds ratio of 3.40 and a 95 per cent confidence interval from 2.88 to 4.01. Young adults came in at 2.90 and senior dogs at 2.24. Puppies had the lowest return risk of any dog age group. For cats the pattern ran the other way at the top end, with senior cats 4.97 times more likely to be returned than kittens.

The reasons for return also varied by age, at p equals 0.002 for dogs. Puppies had lower rates of return for destructive behaviour. Young adults were returned more often for being destructive indoors and for being too active. Senior dogs were returned more often for reasons connected to the owner’s health or the animal’s.

Across all dogs, the two dominant reasons were behavioural issues at 36.1 per cent and incompatibility with existing pets at 18.3 per cent. Those two account for more than half of all returns, and both are things you can investigate before you commit rather than discover afterwards.

The number that changes the moral weight of the decision

One finding in that paper deserves separating out, because it turns an abstract choice into something with consequences.

Returned adult dogs had approximately four times the odds of euthanasia compared with returned puppies, with an odds ratio of 3.94 and a confidence interval from 2.04 to 7.59. Dogs of pit bull type were 2.60 times more likely to be euthanised after return.

Set against that, 80.3 per cent of returned dogs were re adopted, and 90.2 per cent of returned cats. Both facts are true simultaneously. A return is not a death sentence, and it is also not a neutral event, and the risk is unevenly distributed towards exactly the animals who were already the hardest to place.

The honest conclusion is not that you should avoid adopting an adult dog. It is that the cost of getting this decision wrong is not borne equally by both options, and that this should raise the standard of thinking you apply before choosing an adult, not lower your willingness to choose one.

What each choice actually buys you

   WHAT YOU TRADE, EITHER WAY

   PUPPY                             ADULT
   -----------------------------     -----------------------------
   You control the socialisation     You can see the adult
   window. AVSAB: first three        temperament in front of you.
   months, sociability outweighs     Nothing is hypothetical.
   fear.

   You cannot see the adult          You did not control the
   temperament. It does not          socialisation window and may
   exist yet.                        never know what happened in it.

   Lower return risk in the          Powell et al. 2021, n = 23,932:
   Powell data. Puppies had the      adult dogs had the GREATEST
   lowest return risk of any         odds of post-adoption return,
   dog age group.                    OR 3.40 (95% CI 2.88 to 4.01).
                                     Young adults OR 2.90.
                                     Senior dogs OR 2.24.

   You do the house training,        House training may be done,
   the biting phase, the nights.     or may never have been taught.

   ---------------------------------------------------------------
   THE UNCOMFORTABLE NUMBER

   In the same study, returned adult dogs had roughly four
   times the odds of euthanasia compared with returned
   puppies (OR 3.94, 95% CI 2.04 to 7.59).

   Overall, 80.3% of returned dogs were re-adopted.
   Both of those are true at once.
   ---------------------------------------------------------------

   Dogs returned for: behavioural issues 36.1%
                      incompatibility with existing pets 18.3%

The case for the puppy, stated properly

The real argument for a puppy is not that puppies are cute. It is that the socialisation window is the one input into a dog’s adult behaviour that an owner can genuinely control, and it happens once.

The American Veterinary Society of Animal Behavior describes the primary socialisation period as the first three months of life, a stage in which sociability outweighs fear, and states that incomplete socialisation during it increases the risk of fear, avoidance and aggression later on. It goes further, asserting that behavioural problems are the number one cause of relinquishment to shelters, and that behavioural issues rather than infectious diseases are the leading cause of death in dogs under three years of age.

That is the case, and it is a strong one, but notice what it demands of you. It is only an advantage if you are actually available during those weeks and intend to use them deliberately. A puppy raised by someone too busy to socialise it has all of the costs of a puppy and none of the benefit, and arrives at adulthood with the same unknowns as a rescue dog plus a house that has been chewed. The new puppy checklist is organised around exactly this point.

The case for the adult, stated properly

The real argument for an adult is not that you are saving a life, though you may be. It is informational. An adult dog’s temperament exists and can be observed. A puppy’s cannot, because it has not happened yet.

Everything you want to know about how a dog behaves around children, cats, other dogs, visitors, traffic and being left alone is either already knowable about an adult or entirely speculative about a puppy. Rescues that use foster homes can tell you how a dog behaves in a house rather than a kennel, which is a far more useful observation than anything a kennel visit produces.

That advantage is only real if you use it. Meeting a dog once, in a kennel, on a good day, and deciding, converts an adult adoption back into a gamble while keeping the elevated return risk from the Powell data. Meet the dog repeatedly. Ask what is known and what is not, and take an honest answer of we do not know as a good sign rather than a bad one.

There is also a measurable welfare argument for getting an adult out of kennels. Gunter and colleagues, publishing in PeerJ in 2019, found cortisol dropped significantly in shelter dogs during short sleepovers in volunteer homes and rebounded when they returned. The first forty eight hours with a rescue dog covers what to do with that dog when it arrives.

Work through this before you meet anything

The question that is not puppy or adult

A third of the difficulty in this decision comes from asking it in the wrong form. The real variables are not age. They are how much of your next three months is genuinely available, how much uncertainty you can tolerate, and what specifically you cannot live with.

The Powell data says behaviour and incompatibility with existing pets account for over half of dog returns. Both of those are answerable in advance. Ask the rescue to assess compatibility with your existing animals properly rather than optimistically. Write down, before you go, the specific behaviours that would make this not work in your house, and show that list to whoever is rehoming the animal. A good rescue will use it. A bad one will tell you it will be fine.

And if you are buying a puppy rather than adopting, the RSPCA’s rule is the one to hold onto: always see the mother and her puppies together, and never buy if you have doubts about the breeder or the situation. It also reports that 87 per cent of the puppy trade calls it receives concern animals bought over the internet, and points buyers towards the Puppy Contract as a way of turning a persuasive conversation into a document.

Related reading

The new puppy checklist, the first thirty days with a puppy and the first eight weeks cover the puppy route. The first forty eight hours with a rescue dog covers the adult route. The breed selector quiz covers the question underneath both.

For the money, the pet cost calculator and the insurance guide are worth doing before rather than after. For the practicalities, pet proofing your home and the pet care plan both belong before arrival.

For reading an animal you do not know, pet body language is the most useful page here, with licking and following you around covering two behaviours that get badly over interpreted in a new dog. If you are weighing a cat instead, the first thirty days with a kitten is the equivalent.

Where these facts come from

Every claim above was read on the source named beside it, on 4 August 2026. The 23,932 animal sample, the 9.2 per cent overall return rate, the 16.3 and 4.2 per cent species figures, every odds ratio and confidence interval quoted, the age related reasons for return with their p values, the 36.1 and 18.3 per cent reason breakdown, the euthanasia odds ratios and the 80.3 and 90.2 per cent re adoption figures come from Powell and colleagues, Scientific Reports, 2021. The primary socialisation period, the sociability outweighs fear description, and the claims about relinquishment and about the leading cause of death in dogs under three come from the AVSAB position statement on puppy socialisation. The cortisol findings come from Gunter and colleagues, PeerJ, 2019. The instruction to see the mother with her puppies, the 87 per cent internet figure and the Puppy Contract reference come from the RSPCA. No figure on this page was written from memory.