246
A. NELSON-SXITH
enhanced amongst a group kept at low temperatures in crowded conditions, when an LD,, of 4 ml/kg was found for the diesel oil (i.e. about
2 ml per duck).
Hartung (1967) found that an oiled duck was under the same
temperature stress a t plus 15°C as a normal duck at minus 20°C;
however, even heavily oiled ducks survived at minus 26°C for as long
as 36 h, provided they had sufficient fat reserves to keep up the high
metabolic activity needed to maintain their body temperature. Mallard
( A . platyrhynchos) in poor condition survived this temperature for only
4 h after being covered with 7 g diesel oil. Adequate food is thus
essential to survival, but in a coastal oil-spill the feeding-grounds are
likely also to be affected by oil. Harrison and Buck (1967) reported
that, although a high sea-bird mortality attended an overnight spill
in the Medway Estuary during the autumn of 1966, the greatest effect
was on the food supply. Surviving birds were forced to leave the area
for the whole of the following winter.
Oil is known to affect the viability of bird eggs. Fuel-oil has been
sprayed onto their eggs in successful attempts to control populations
of gulls Larus spp. and cormorants Phalacrocorax carbo (L.) (Gross,
1950). In experiments by Hartung (1965b), duck eggs treated with 236 mg medicinal oil (presumably non-toxic) showed a hatchability of
20y0 as against 90% in controls ; only one egg treated with more than
12 mg subsequently hatched. The undersides of ducks were then
smeared with 4-5 ml of the oil before setting them to incubate fresh
fertile eggs; of 19 eggs, none hatched. Rittinghaus (1956) reported an
incident in which the eggs of numerous terns (Sterna sandvicensis
Latham) and other shore birds failed to hatch after the parents had
become contaminated with stranded oil, and Jouanin (1967) observed
that gannets Sula bassana (L.) (which are normally unaffected by
floating oil, since they dive only on prey that they can see) were fouling
themselves and their eggs by collecting oiled seaweed as material for
building nest-mounds. Hartung (1965b) further found that a single
dose of lubricating oil, fed at 2g/kg, immediately halted laying and
suppressed reproductive behaviour.
2. Mammals
Aquatic mammals are in somewhat the same situation as diving
birds. They return to the surface at intervals to breathe and most of
them have fur which readily traps oil, thereby losing its property of
heat-insulation. Fewer accounts have been published, but Peller (1963)
records the oiling of muskrats (Ondatra sp.), beavers (Castor Jiber L.)
and even deer, while Wragg (1954) observed that fuel-oil used as a
A. NELSON-SXITH
enhanced amongst a group kept at low temperatures in crowded conditions, when an LD,, of 4 ml/kg was found for the diesel oil (i.e. about
2 ml per duck).
Hartung (1967) found that an oiled duck was under the same
temperature stress a t plus 15°C as a normal duck at minus 20°C;
however, even heavily oiled ducks survived at minus 26°C for as long
as 36 h, provided they had sufficient fat reserves to keep up the high
metabolic activity needed to maintain their body temperature. Mallard
( A . platyrhynchos) in poor condition survived this temperature for only
4 h after being covered with 7 g diesel oil. Adequate food is thus
essential to survival, but in a coastal oil-spill the feeding-grounds are
likely also to be affected by oil. Harrison and Buck (1967) reported
that, although a high sea-bird mortality attended an overnight spill
in the Medway Estuary during the autumn of 1966, the greatest effect
was on the food supply. Surviving birds were forced to leave the area
for the whole of the following winter.
Oil is known to affect the viability of bird eggs. Fuel-oil has been
sprayed onto their eggs in successful attempts to control populations
of gulls Larus spp. and cormorants Phalacrocorax carbo (L.) (Gross,
1950). In experiments by Hartung (1965b), duck eggs treated with 236 mg medicinal oil (presumably non-toxic) showed a hatchability of
20y0 as against 90% in controls ; only one egg treated with more than
12 mg subsequently hatched. The undersides of ducks were then
smeared with 4-5 ml of the oil before setting them to incubate fresh
fertile eggs; of 19 eggs, none hatched. Rittinghaus (1956) reported an
incident in which the eggs of numerous terns (Sterna sandvicensis
Latham) and other shore birds failed to hatch after the parents had
become contaminated with stranded oil, and Jouanin (1967) observed
that gannets Sula bassana (L.) (which are normally unaffected by
floating oil, since they dive only on prey that they can see) were fouling
themselves and their eggs by collecting oiled seaweed as material for
building nest-mounds. Hartung (1965b) further found that a single
dose of lubricating oil, fed at 2g/kg, immediately halted laying and
suppressed reproductive behaviour.
2. Mammals
Aquatic mammals are in somewhat the same situation as diving
birds. They return to the surface at intervals to breathe and most of
them have fur which readily traps oil, thereby losing its property of
heat-insulation. Fewer accounts have been published, but Peller (1963)
records the oiling of muskrats (Ondatra sp.), beavers (Castor Jiber L.)
and even deer, while Wragg (1954) observed that fuel-oil used as a