Jeremy Bentham claimed that private property has ‘given to man the empire of the earth.’ One of the great advantages of private over common property is that, to use the economic jargon, it “internalises externalities.” Rendered in normal language, this means that an owner reaps what he sows. Thus, an owner either enjoys the benefits of judicious investment and prudent husbandry or suffers the baleful effects of underinvestment or overexploitation.

Because the right of, for instance, an owner in fee simple is termless, he or she can make investment decisions that may only bear fruit in the long term. As Ellickson has noted, that such rights can be devised to an owner’s children, or other loved ones, promotes the responsible management of scarce resources across generations. To again use the economic jargon, termless ownership rights give owners a “low discount rate”. This is not true of more limited rights, such as bailments. As the economist Larry Summers has quipped, “[i]n the history of the world, no one has ever washed a rented car.”

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Termless rights are not the only reason that private property encourages socially desirable investment in scarce resources. As Lisa Austin has argued, a central, feature of private property is that an owner is entitled to put something down and pick it up again later. In contrast to the norms that govern children’s play equipment, owners do not forfeit their rights to objects that they no longer possess. In my recently published book on possession, I describe this as the principle of “disaggregation”. This principle recognises that, although property rights are created by acts of possession, their validity, as Luke Rostill has also noted, does not depend upon ongoing physical control. Were it otherwise, those who acquire rights through possession would either not invest, or would inefficiently tether themselves to tangible resources for fear that, in their absence, their hard-won gains would be captured by rent-seekers. Although the principle of “disaggregation” may seem obvious now, as Honoré observed in his famous essay on ownership, ‘ [t]o have worked out the notion of “having a right to” as distinct from merely “having” … was a major intellectual achievement’.

What, however, if the resource in question were not land but fish? Does the principle of “disaggregation” still apply? That was the question for the Court of Appeal in Borwick. The appellant, BDS, was the freehold owner of several man-made ponds that it stocked with fish and operated as a recreational “catch and release” facility. In 2016, the land was sold to CWF under a mortgagee’s power of sale. Although the fish were worth more than £1m, the contract of sale made no mention of them. Following the sale of the land, BDS sued CWF, claiming conversion of the fish. 

Had the dispute concerned something other than fish, its resolution would have been simple. Conveyances of real property pass only the “realty”, a term that includes both the land and anything “affixed” to it. Absent agreement to the contrary, a purchaser of land does not acquire the vendor’s title to chattels that she happens to leave behind. The dispute in Borwick was complicated by the fact that fish, whilst certainly not realty, are not chattels either. Following a distinction of ancient provenance, fish are considered to be wild by nature or, in legal parlance, “ferae naturae”. Unlike pet dogs and other domestic animals that are considered “domitae naturae”, one can only obtain ownership of wild animals by killing or mortally wounding them. Whilst they are alive, the law recognises only “qualified property” in them. 

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For instance, a landowner has certain rights over wild animals that arise “ratione soli”; by “reason of the soil”. A right acquired “ratione soli” does not merely afford the landowner the exclusive liberty to hunt wild animals that happen to be on his land. It also provides that any wild animal killed by a trespasser becomes property of the landowner. To encourage the rearing of non-sedentary wild animals, the law also grants limited ownership rights over wild animals that have been tamed by, to use Blackstone’s phrase, “art, industry and education”. The right “per industriam” allows an apiarist, for instance, who has invested time and skill in rearing bees to bring a claim against anyone interferes with them, but only for so long as they remain in his “possession” or have the “intention” of returning to the hive. If a wild animal either regains its “natural liberty” or loses the habit of returning, it once again becomes ownerless or, to use the Latin tag, “res nullius”.

All three judges of the Court of Appeal held that BDS’s claim for conversion failed. This was not because the conveyance of the land passed title to the fish to CWF as purchaser. It was instead because BDS’s qualified right to the fish, whether it arose ratione soli or per industriam, ended when the land was transferred to CWF. After execution of the conveyance, CWF’s control over the ponds gave it possession of, and thus a qualified right to, the fish that remained in them.   

As the Court noted, BDS had invested a great deal of time and money in stocking the ponds and raising the fish, some of which had become so large that they acquired affectionate sobriquets. However, because BDS’s rights to the fish depended on its ongoing control over the ponds in which they lived, it failed to capture all the gains on its investment. CWF reaped what it did not sow because fish and other animals that are classified as ferae naturae do not follow the principle of disaggregation. The obvious question is: why not?

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An answer is found in Bob Ellickson’s famous essay on comparative whaling norms, in which he argued that whalers efficiently adapted their property norms to suit the conditions of individual fisheries. Although, in all fisheries, rights to whales were allocated to the ship that successfully launched the first harpoon, those rights were often subject to differing conditions of defeasance. In some fisheries, the existence of a whaler’s right, once acquired, might depend on the whale remaining tethered to the ship. In others, it might depend on the ship maintaining active pursuit of its quarry. These conditions of defeasance were not arbitrary, but reflected an attempt by close-knit whaling communities to create rules that were not only simple to apply, but also discouraged free-riding whilst ensuring that other ships had sufficient incentive to pursue whales, or whale carcasses, that had eluded the original captor.

Ellickson’s efficiency argument can also be applied to fish and other animals that are ferae naturae. A right per industriam allows a pigeon fancier, for instance, to maintain conversion against someone who interferes with her pigeons, but only for so long as they are in her possession or habitually return to the coop. If her pigeons make a successful bid for freedom, then they become ownerless. Whilst this may disappoint the pigeon fancier, the impossibility of her ever finding the pigeons renders the existence of any ongoing property right pointless. In any case, like bees that refuse to return to their hive, homing pigeons that refuses to “home” are of little use to the fancier.

Likewise, BDS’s limited rights over its fish, whether they arose per industriam through its husbandry or ratione soli by virtue of its ownership of the ponds, were also sufficient for its purposes. If a trespasser had killed the fish, BDS would have an action against the trespasser, and title to the fish, as normal chattels, would automatically vest in BDS. If a “fish liberationist” had taken the fish and released them into a local stream, then BDS would have an action against the liberator for conversion of the fish, but would not retain ownership of the fish which, having regained their “natural liberty”, would once again became res nullius. As with a pigeon fancier’s pigeons, the impossibility of identifying and recapturing the fish makes the existence of an enduring property right pointless. Its only effect would be to make a tortfeasor out of any angler who subsequently caught one of them. 

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The unfortunate circumstance in which BDS found itself was not due to a defect in the property law’s treatment of wild animals. As the Court noted, prior to the sale of the land to CWF, BDS was at liberty to either remove the fish from the ponds or, alternatively, to include an additional sum in the sale price should CWF have wished to purchase them. Neither option was pursued because, as the Court noted, the sale process was controlled by BDS’s mortgagee, and not BDS itself. Presumably an owner would have been more attentive to its own interests. 

The facts in Borwick required the Court to grapple with some of the more obscure doctrines of personal property law. As is true of other famous cases, what is significant about Borwick is not its unusual subject matter, but what it tells us about the law more generally. Although the distinction between wild and domestic animals might, on first blush, appear arbitrary, it actually demonstrates that the common law is an evolved order that very often, if not always, displays a fundamental rationality.


How to cite this blog post (Harvard style) 

Crawford, M. (2020). Wild Things: Borwick Development Solutions v Clear Water Fisheries [2020] EWCA Civ 578. Available at: (Accessed [date]).