CHAPTER 7 Modes of
Feeding
Foods and Feeding Mammals, like all organisms, require energy and nutrients for mainte-
Insectivorous nance, growth, activity, and reproduction—t hat is, for survival. Main-
Carnivorous taining a high body temperature, which is a key feature of Class Mam-
Herbivorous malia, requires regular acquisition of food. The food of mammals
Omnivory ranges from microscopic forms such as diatoms and crustaceans—a sta-
ple in the diet of the largest mammals, the baleen whales—to seden-
Foraging Strategies tary forms such as plants used by the most abundant mammals, the
Optimal Foraging rodents. Mammals consume food of high-energy content (blood of
Marginal Value Theorem vertebrates and insects) as well as of low-energy value (grasses and
Food-Hoarding stems). The food of mammals may be highly specialized and restricted
(nectar of localized plants) or rather general and readily available (grasses
and herbs). To meet their high-energy needs, mammals have evolved a
diverse array of trophic, or nutritional, specializations. The adaptive
radiation in food-gathering morphologies is diverse and reflects the
diversity of available food.
In this chapter, we detail the feeding apparatus of mammals, focus-
ing on the capturing (teeth, tongue, and jaw musculature) and pro
cessing (alimentary canal) of food. Feeding integrates the sense or-
gans and locomotor adaptations (see Chapter 6). Although different
orders of mammals are sometimes grouped according to their modes of
feeding (i.e., Carnivora), food habits cannot be employed as a system-
atic criterion because many members of an order may depart from
t hese feeding generalizations. Thus, to enhance understanding of nu-
tritional adaptations, we suggest consulting specific chapters to unite
anatomical specializations of different groups with their dietary habits.
At the end of the chapter, we w ill briefly examine some general princi
ples regarding mammalian foraging strategies.
Foods and Feeding
We understand the life-history traits and food habits of extant mam-
mals by examining their teeth. As discussed in Chapter 4, all mam-
130
, Chapter 7 Modes of Feeding 131
O
Q
M
E
P
Increasingly advanced
N
D L
insectivores
Gnawing Grazing and
herbivores browsing herbivores
C K
Omnivores
H G
B Increasingly advanced
carnivores
Specialized
insectivores
T F
A
Primitive (basal) insectivores
Plankton specialists
Fruit specialists
S Fish and
Nectar specialists I
Mollusk squid specialists
specialists R J
Figure 7.1 Skull and dentition specialization. Feeding specializations in the dentition and skulls of mammals relate to their
dietary habits: (A) hedgehog; (B) mole; (C) armadillo; (D) anteater; (E) giant anteater; (F) marmoset; (G) peccary; (H) bear; (I) fruit-
eating bat; (J) nectar-eating bat; (K) raccoon; (L) coyote; (M) mountain lion; (N) horse; (O) deer; (P) jackrabbit; (Q) woodrat;
(R) porpoise; (S) right whale; (T) walrus. Adapted from Rogers (1986).
mals, except certain whales, monotremes, and anteaters, oday, this feeding niche is exploited by members of nine
T
have teeth, and these structures are inextricably linked orders of mammals: echidnas and the platypus (Order
with food habits. As mammals evolved in the Mesozoic, Monotremata); marsupial moles (Order Notoryctemor-
major changes occurred in their dentition and jaw muscu- phia), solenodons, hedgehogs, shrews, moles, and desmans
lature; teeth became differentiated to perform specialized (Order Eulipotyphla); most bats (Order Chiroptera); ant-
functions. Within extant species, several trophic groups eaters and armadillos (Orders Cingulata and Pilosa); pan-
can be recognized—namely, insectivorous, carnivorous, golins (Order Pholidota); aardvarks (Order Tubulidentata);
herbivorous, and omnivorous mammals. Other special- and the aardwolf (Order Carnivora; see Figure 7.1). Many
ized modes of feeding have evolved from t hese four basic other orders of mammals also have members that exhibit
plans (Figure 7.1). insectivorous habits. The dentition of hedgehogs, shrews,
moles, and most bats is typified by numerous sharp teeth
with sharp cones and blades for piercing, shearing, and ul-
INSECTIVOROUS timately crushing the tough chitinous exoskeletons of in-
sects. In many forms, the lower incisors are slightly pro-
Insectivory cumbent (pointing forward and upward) to aid in grasping
prey (see Figure 7.1). Because insectivorous mammals con-
Mammals that consume insects, other small arthropods, sume minimal amounts of fibrous vegetative material,
or worms are referred to as insectivorous (meaning prolonged fermentation is not required; their alimentary
“insect-eating”). We know from examination of Triassic canals are short, and most insectivores and chiropterans
mammals that the insectivorous feeding niche represented lack a cecum (Figure 7.2).
the primitive, or basal, condition of eutherian mammals.
, 132 Part 2 Structure and Function
A Insectivore B Carnivore C Nonruminant herbivore D Ruminant herbivore
Esophagus Stomach
Stomach
Stomach
Esophagus Rumen
Cecum Reticulum Abomasum
Omasum
Anus
Short intestine and
Anus colon, small cecum Cecum
Short intestine,
no cecum
Anus
Simple stomach, Cecum
large cecum
Anus
Four-chambered stomach
with large rumen, long
small and large intestine
Figure 7.2 Digestive system. The digestive systems of mammals, illustrating the differences in morphology that correspond to
different diets: (A) short-tailed shrew; (B) red fox; (C) black-tailed jackrabbit; (D) mule deer.
Aerial Insectivores
more than their body mass (Kurta et al. 1990; Kurta 2017).
The most abundant foods are plants and insects; it is there- Throughout their range, insectivorous bats feed on a di-
fore not surprising that the most abundant mammals are verse array of arthropods, ranging from scorpions, spiders,
rodents and bats. Chiropterans occupy ecological niches in and crustaceans to soft-bodied and hard-bodied insects
almost all habitats of the world; the diversity of their diets (Whitaker 1994b; Neuweiler 2000; Schulz 2000; McWil-
is unparalleled among extant mammals. The majority liams 2005; Dodd et al. 2012; Moosman et al. 2012; Cole-
(70%) of “microchiropterans” (see Chapter 21 for current man and Barclay 2013; McCraken et al. 2018). North
terminology associated with this group) is insectivorous American bats, namely, the little brown bat (Myotis lucifu-
(Black 1974; Whitaker 1988; Whitaker et al. 1996; Neu- gus) and big brown bat, are major consumers of mosqui-
weiler 2000; Patterson et al. 2003; Gonsalves et al. 2013; toes. Recent evidence derived from maternity roosts of M.
Nelson and Gillam 2017). All bats residing north of 38°N lucifugus and E. fuscus in Wisconsin indicate that taxonomic
and south of 40°S latitude are insectivorous. Bats may con- richness of mosquitoes is higher than previously shown
sume 50% of their body mass in insects each night. For (Wray et al. 2018).
example, lactating female big brown bats (Eptesicus fuscus) Insectivorous bats are voracious eaters: Mexican free-
nightly consume a quantity of insects that is equivalent to tailed bats (Tadarida brasiliensis) in central Texas, totaling
Feeding
Foods and Feeding Mammals, like all organisms, require energy and nutrients for mainte-
Insectivorous nance, growth, activity, and reproduction—t hat is, for survival. Main-
Carnivorous taining a high body temperature, which is a key feature of Class Mam-
Herbivorous malia, requires regular acquisition of food. The food of mammals
Omnivory ranges from microscopic forms such as diatoms and crustaceans—a sta-
ple in the diet of the largest mammals, the baleen whales—to seden-
Foraging Strategies tary forms such as plants used by the most abundant mammals, the
Optimal Foraging rodents. Mammals consume food of high-energy content (blood of
Marginal Value Theorem vertebrates and insects) as well as of low-energy value (grasses and
Food-Hoarding stems). The food of mammals may be highly specialized and restricted
(nectar of localized plants) or rather general and readily available (grasses
and herbs). To meet their high-energy needs, mammals have evolved a
diverse array of trophic, or nutritional, specializations. The adaptive
radiation in food-gathering morphologies is diverse and reflects the
diversity of available food.
In this chapter, we detail the feeding apparatus of mammals, focus-
ing on the capturing (teeth, tongue, and jaw musculature) and pro
cessing (alimentary canal) of food. Feeding integrates the sense or-
gans and locomotor adaptations (see Chapter 6). Although different
orders of mammals are sometimes grouped according to their modes of
feeding (i.e., Carnivora), food habits cannot be employed as a system-
atic criterion because many members of an order may depart from
t hese feeding generalizations. Thus, to enhance understanding of nu-
tritional adaptations, we suggest consulting specific chapters to unite
anatomical specializations of different groups with their dietary habits.
At the end of the chapter, we w ill briefly examine some general princi
ples regarding mammalian foraging strategies.
Foods and Feeding
We understand the life-history traits and food habits of extant mam-
mals by examining their teeth. As discussed in Chapter 4, all mam-
130
, Chapter 7 Modes of Feeding 131
O
Q
M
E
P
Increasingly advanced
N
D L
insectivores
Gnawing Grazing and
herbivores browsing herbivores
C K
Omnivores
H G
B Increasingly advanced
carnivores
Specialized
insectivores
T F
A
Primitive (basal) insectivores
Plankton specialists
Fruit specialists
S Fish and
Nectar specialists I
Mollusk squid specialists
specialists R J
Figure 7.1 Skull and dentition specialization. Feeding specializations in the dentition and skulls of mammals relate to their
dietary habits: (A) hedgehog; (B) mole; (C) armadillo; (D) anteater; (E) giant anteater; (F) marmoset; (G) peccary; (H) bear; (I) fruit-
eating bat; (J) nectar-eating bat; (K) raccoon; (L) coyote; (M) mountain lion; (N) horse; (O) deer; (P) jackrabbit; (Q) woodrat;
(R) porpoise; (S) right whale; (T) walrus. Adapted from Rogers (1986).
mals, except certain whales, monotremes, and anteaters, oday, this feeding niche is exploited by members of nine
T
have teeth, and these structures are inextricably linked orders of mammals: echidnas and the platypus (Order
with food habits. As mammals evolved in the Mesozoic, Monotremata); marsupial moles (Order Notoryctemor-
major changes occurred in their dentition and jaw muscu- phia), solenodons, hedgehogs, shrews, moles, and desmans
lature; teeth became differentiated to perform specialized (Order Eulipotyphla); most bats (Order Chiroptera); ant-
functions. Within extant species, several trophic groups eaters and armadillos (Orders Cingulata and Pilosa); pan-
can be recognized—namely, insectivorous, carnivorous, golins (Order Pholidota); aardvarks (Order Tubulidentata);
herbivorous, and omnivorous mammals. Other special- and the aardwolf (Order Carnivora; see Figure 7.1). Many
ized modes of feeding have evolved from t hese four basic other orders of mammals also have members that exhibit
plans (Figure 7.1). insectivorous habits. The dentition of hedgehogs, shrews,
moles, and most bats is typified by numerous sharp teeth
with sharp cones and blades for piercing, shearing, and ul-
INSECTIVOROUS timately crushing the tough chitinous exoskeletons of in-
sects. In many forms, the lower incisors are slightly pro-
Insectivory cumbent (pointing forward and upward) to aid in grasping
prey (see Figure 7.1). Because insectivorous mammals con-
Mammals that consume insects, other small arthropods, sume minimal amounts of fibrous vegetative material,
or worms are referred to as insectivorous (meaning prolonged fermentation is not required; their alimentary
“insect-eating”). We know from examination of Triassic canals are short, and most insectivores and chiropterans
mammals that the insectivorous feeding niche represented lack a cecum (Figure 7.2).
the primitive, or basal, condition of eutherian mammals.
, 132 Part 2 Structure and Function
A Insectivore B Carnivore C Nonruminant herbivore D Ruminant herbivore
Esophagus Stomach
Stomach
Stomach
Esophagus Rumen
Cecum Reticulum Abomasum
Omasum
Anus
Short intestine and
Anus colon, small cecum Cecum
Short intestine,
no cecum
Anus
Simple stomach, Cecum
large cecum
Anus
Four-chambered stomach
with large rumen, long
small and large intestine
Figure 7.2 Digestive system. The digestive systems of mammals, illustrating the differences in morphology that correspond to
different diets: (A) short-tailed shrew; (B) red fox; (C) black-tailed jackrabbit; (D) mule deer.
Aerial Insectivores
more than their body mass (Kurta et al. 1990; Kurta 2017).
The most abundant foods are plants and insects; it is there- Throughout their range, insectivorous bats feed on a di-
fore not surprising that the most abundant mammals are verse array of arthropods, ranging from scorpions, spiders,
rodents and bats. Chiropterans occupy ecological niches in and crustaceans to soft-bodied and hard-bodied insects
almost all habitats of the world; the diversity of their diets (Whitaker 1994b; Neuweiler 2000; Schulz 2000; McWil-
is unparalleled among extant mammals. The majority liams 2005; Dodd et al. 2012; Moosman et al. 2012; Cole-
(70%) of “microchiropterans” (see Chapter 21 for current man and Barclay 2013; McCraken et al. 2018). North
terminology associated with this group) is insectivorous American bats, namely, the little brown bat (Myotis lucifu-
(Black 1974; Whitaker 1988; Whitaker et al. 1996; Neu- gus) and big brown bat, are major consumers of mosqui-
weiler 2000; Patterson et al. 2003; Gonsalves et al. 2013; toes. Recent evidence derived from maternity roosts of M.
Nelson and Gillam 2017). All bats residing north of 38°N lucifugus and E. fuscus in Wisconsin indicate that taxonomic
and south of 40°S latitude are insectivorous. Bats may con- richness of mosquitoes is higher than previously shown
sume 50% of their body mass in insects each night. For (Wray et al. 2018).
example, lactating female big brown bats (Eptesicus fuscus) Insectivorous bats are voracious eaters: Mexican free-
nightly consume a quantity of insects that is equivalent to tailed bats (Tadarida brasiliensis) in central Texas, totaling
