Respiratory anatomy in the pangolin is shaped by three competing demands that rarely coexist in other mammals: the need for highly sensitive chemosensory olfaction to locate buried insect colonies; the requirement to temporarily exclude all airflow during excavation of dusty, chemically hostile termite mounds; and the physiological cost of thermoregulating a poorly-insulated body in environments ranging from equatorial rainforest to semi-arid savannah. This article traces pangolin respiratory anatomy from the external nares to the alveolar surface, examining structural adaptations at each level and their functional consequences for both wild and captive animals.
External Nares and Nasal Vestibule
The pangolin's nostrils are small, slit-like external nares positioned at the rostral tip of the elongated snout. Unlike the broadly flared nares of many macrosmatic mammals, they are encircled by a ring of well-developed dilator and constrictor muscle groups. This musculature, innervated by branches of the facial nerve, enables complete voluntary occlusion of the nasal airway — a capability pangolins exploit extensively during termite mound excavation. Closure is not passive: electromyographic recordings from captive Manis pentadactyla demonstrate active muscle firing coordinated with tongue-projection sequences, meaning the animal effectively alternates between breath-holding foraging bouts and brief surface-emergence ventilation intervals.
Nasal Turbinates and Olfactory Mucosa
Behind the vestibule, the nasal passage expands into a chamber housing three scroll-shaped turbinate bones — the dorsal, middle, and ventral nasoturbinates — plus the ethmoid turbinates more caudally. Pangolin turbinate surface area is substantially larger relative to snout volume than in non-myrmecophagous mammals of comparable size, a pattern shared with other highly olfaction-dependent species like dogs and shrews. The expanded surface serves two purposes simultaneously: warming and humidifying incoming air to protect delicate lower airway mucosa from temperature and aridity extremes, and providing the large olfactory epithelial area required for sensitive detection of volatile insect-colony chemical signals.
Olfactory Epithelium Distribution
The olfactory epithelium — a pseudostratified neuroepithelium bearing olfactory receptor neurons — lines the ethmoid turbinates and much of the dorsal nasal cavity. In pangolins, olfactory receptor gene family size is moderate compared with canids but substantial compared with primates, consistent with reliance on olfaction for prey localisation but not social chemosensory communication to the degree seen in many rodents. The olfactory epithelium transitions abruptly to respiratory epithelium at the level of the middle turbinate, where the mucociliary escalator — a coordinated ciliary beating system driving mucus rostrally toward the pharynx — begins its protective function.
Nasolacrimal Duct Adaptations
A notable feature of pangolin nasal anatomy is the enlarged nasolacrimal duct that drains tear film from the medial canthus of each eye into the ventral nasal meatus. Scale-covered eyelids in pangolins — and the thickened nictitating membrane — generate relatively large volumes of tear fluid during blinking, and the nasolacrimal system is correspondingly robust. This drainage reaches the nasal vestibule and contributes a watery component to nasal secretions that may assist in humidifying inspired air during high-activity periods.
Nasopharynx and Larynx
Air passes from the choanae (posterior nasal openings) into the nasopharynx, a short chamber where the respiratory and digestive pathways intersect before the larynx establishes the respiratory-specific channel. The pangolin larynx is anatomically conventional for a small to medium mammal: cricoid, thyroid, and arytenoid cartilages surrounding the glottis, with the epiglottis providing the flap that deflects food into the oesophagus during swallowing. Uniquely, the pangolin's extraordinary tongue mechanism creates an unusual anatomical constraint at the larynx: the hyoid apparatus, which anchors the tongue's proximal musculature, extends caudally into the thoracic cavity in all pangolin species, passing alongside or beneath the larynx. This means the laryngeal cartilages are in intimate proximity to the proximal tongue musculature, and vigorous tongue-projection movements during active foraging are accompanied by simultaneous laryngeal displacement — a co-evolution of the digestive and respiratory systems that has no close parallel in other mammals.
Trachea and Bronchial Tree
The trachea descends from the larynx through the cervical region and into the thoracic inlet, bifurcating at the carina into left and right principal bronchi. In pangolins, the tracheal rings are complete C-shaped cartilage rings — a feature shared with some rodents and unlike the D-shaped incomplete rings of carnivores — providing rigid airway support during the forceful nostril-occlusion and intra-thoracic pressure changes of burrowing. Tracheal length is proportionally longer relative to body length than in most comparably sized mammals, a consequence of the elongated neck and thorax that accommodates the retrosternal hyoid and tongue anatomy.
Bronchial Architecture
The principal bronchi divide into lobar bronchi supplying each lung lobe, which in turn branch progressively into segmental bronchi, subsegmental bronchi, bronchioles, terminal bronchioles, and finally respiratory bronchioles transitioning to alveolar ducts. The branching pattern follows a broadly dichotomous model, though asymmetric branching with unequal daughter-branch diameters is common, consistent with the pattern seen in most mammals. The airway epithelium transitions progressively from ciliated pseudostratified columnar epithelium in the bronchi to cuboidal bronchiolar epithelium and finally to the very thin squamous type II pneumocyte-lined alveolar surface.
Mucus and Mucociliary Clearance
Goblet cells in the bronchial epithelium and submucosal glands in the larger bronchi continuously secrete a two-phase mucus layer: a sol phase (periciliary fluid) allowing ciliary beat and a gel phase (mucus proper) that traps particulates. In a foraging pangolin, the nasal passages and proximal airways are repeatedly exposed to fine soil particles, fungal spores from termite fungal gardens, and insect chitin fragments — all of which must be trapped and cleared before reaching the alveoli. The mucociliary escalator carries this particulate-laden mucus rostrally toward the oropharynx where it is swallowed. Mucociliary clearance rate in pangolins has not been directly measured, but the high goblet cell density reported in histological sections suggests a vigorous secretory capacity appropriate to the dusty foraging environment.
Lung Gross Anatomy and Lobation
The lungs are paired, spongy organs filling the pleural cavities on either side of the mediastinum. In pangolins, the right lung is larger than the left and divided into more lobes, following the general mammalian asymmetry imposed by the left-sided cardiac bulge displacing the left lung. In Manis javanica specimens that have been described, the right lung has four lobes (cranial, middle, accessory or mediastinal, and caudal) and the left lung three (cranial, middle, and caudal). Some inter-species variation in lobation pattern exists across the pangolin family, but the basic four-right/three-left or similar arrangements are conserved.
| Species | Right Lobes | Left Lobes | Notes |
|---|---|---|---|
| Manis javanica | 4 | 3 | Best documented; accessory lobe present |
| Manis pentadactyla | 4 | 3 | Similar to M. javanica |
| Smutsia temminckii | 4 | 2–3 | Left middle lobe variable |
| Phataginus tricuspis | 3–4 | 2–3 | Limited specimens available |
The lungs are encased in the visceral pleura and fill the thoracic cavity when inflated. At rest, the diaphragm maintains a dome shape that rises into the caudal thorax, and the functional residual capacity — the volume of air remaining after passive expiration — is broadly comparable to values in insectivores of similar mass. Total lung capacity relative to body mass has not been rigorously quantified in pangolins under standardised conditions, but respiratory rate measurements in anaesthetised individuals suggest a moderate respiratory rate of 15–25 breaths per minute in resting adults, consistent with metabolic rates somewhat lower than equivalent-mass carnivores.
Alveolar Architecture and Gas Exchange
The alveoli are the terminal functional units of the lung, thin-walled sacs across whose epithelium oxygen and carbon dioxide diffuse down partial pressure gradients. Pangolin alveolar walls contain the two principal cell types: type I pneumocytes (flattened, covering 95% of alveolar surface, primary gas exchange cells) and type II pneumocytes (cuboidal, producing surfactant). Pangolin surfactant composition has not been characterised in detail, but the surface-active phospholipid mixture is presumed to follow the mammalian default of dipalmitoylphosphatidylcholine (DPPC) as the primary component, reducing alveolar surface tension and preventing collapse at end-expiration.
Pulmonary Capillary Density
Surrounding each alveolus, a dense network of pulmonary capillaries brings deoxygenated blood from the right ventricle into intimate proximity with alveolar air across an air–blood barrier of only 0.3–0.5 µm thickness. Morphometric estimates of capillary density in mammalian lungs generally scale inversely with body mass, meaning smaller species have higher capillary densities and faster oxygen diffusion per unit lung volume. Pangolins fall in a mid-range body mass bracket (1–35 kg depending on species), and their capillary density is presumably intermediate, adequate for their relatively low-intensity, endurance-based foraging lifestyle rather than the burst aerobic demands of cursorial predators.
Respiratory Mechanics and Breathing During Burrowing
Burrowing and subsurface foraging impose unusual mechanical constraints on respiration. When a pangolin forces its snout deep into a compacted termite mound or subterranean tunnel, thoracic compression from surrounding soil and the physically demanding excavation musculature alter the normal pressure relationships of the thoracic cavity. Pangolins likely employ periods of complete breath-holding — diaphragm fixation with glottis closure — to stabilise the thoracic cavity as a rigid platform during peak excavation forces, analogous to the Valsalva-like manoeuvres used by humans during heavy lifting. Between these fixation events, rapid ventilatory cycles restore blood-gas homeostasis before the next excavation sequence.
Thermoregulatory Panting
Pangolins have a poorly insulated ventral surface (the scale-free underside) and limited sweat gland density. Evaporative cooling from the respiratory tract — panting — therefore plays a significant thermoregulatory role in hot conditions. African ground pangolins in particular, occupying open savannah exposed to direct solar radiation, may pant visibly when overheated. Panting converts the normal slow deep ventilation pattern to rapid shallow breaths at high frequency, maximising evaporative cooling from the upper airway surfaces while minimising the CO₂ washout that would accompany deep hyperventilation — a thermoregulatory refinement also seen in domestic dogs.
Respiratory Pathology in Captive Pangolins
Bacterial Pneumonia
The commensals of the termite mound soil — gram-negative enterobacteria, Pseudomonas, Klebsiella pneumoniae, and oral flora including Pasteurella — are part of the wild pangolin's normal microbial environment, against which its intact mucociliary and immune defences maintain equilibrium. In captivity, stress-driven glucocorticoid elevation suppresses mucociliary beat frequency and reduces pulmonary macrophage activity, allowing colonisers that the healthy wild lung would clear to establish bronchopneumonia. The cranioventral lung distribution typical of aspiration and hypostatic pneumonia is common in debilitated individuals unable to maintain normal posture.
Fungal Pneumonia
Aspergillus fumigatus and related thermotolerant fungi present on organic bedding material — hay, wood shavings, decaying plant matter — represent a hazard in captive enclosures that wild pangolins rarely encounter at infectious densities. Aspergillosis causes granulomatous pneumonia that, once established, responds poorly to antifungal treatment in pangolins whose hepatic drug metabolism may be poorly characterised. The olfactory route — inhalation of conidia trapped in the nasal mucosa — is particularly relevant given the large olfactory epithelial surface area and the humid conditions of nasal mucus that support germination.
Aspiration Pneumonia
Feeding pangolins by syringe or tube with liquid dietary formulas — a common approach in rehabilitation centres unfamiliar with pangolin physiology — risks aspiration of formula into the airway if the animal is stressed or uncooperative. The elongated soft palate, which must be displaced during tube-feeding, and the intimate anatomical proximity of the larynx to the hyoid-tongue system create aspiration risk that is higher than in many other mammals. Aspiration of even small liquid volumes triggers chemical pneumonitis followed by bacterial superinfection in the oxygen-rich pulmonary environment.
Pulmonary Surfactant and Prematurity Risk
Pangolins typically give birth to a single pup per pregnancy. Neonatal pangolins are born with scales still soft and body systems immature; pulmonary surfactant production by type II pneumocytes is not fully established until shortly before term. Premature or neonatal animals that have experienced perinatal stress may show surfactant deficiency with alveolar collapse, analogous to infant respiratory distress syndrome in humans. This adds a paediatric respiratory vulnerability to the already challenging task of hand-rearing neonatal pangolins, and artificial surfactant supplementation is among the interventions under investigation in specialist facilities.
Frequently Asked Questions
- How do pangolins breathe while foraging inside termite mounds?
- Pangolins use active muscular closure of the nostrils during foraging bouts, temporarily halting airflow and preventing dust, soil particles, and insect defensive secretions from entering the lower airways. Breath-holding capacity during excavation bouts has been estimated at 60–90 seconds in some studies.
- What lung diseases are most common in captive pangolins?
- Bacterial pneumonia (Klebsiella, Pasteurella, Pseudomonas) and fungal pneumonia (Aspergillus) are the leading respiratory causes of captive mortality. Chronic aspiration pneumonia from inappropriate liquid feeding is also documented. Reduced mucociliary clearance under captive stress predisposes the lungs to all three.
- Do pangolins have a diaphragm?
- Yes. Pangolins possess a fully developed musculotendinous diaphragm as the primary inspiratory muscle, as in all placental mammals. The dome-shaped diaphragm contracts and flattens during inspiration, enlarging thoracic volume. Intercostal muscles provide secondary respiratory drive, particularly during burrowing when thoracic compression from soil pressure modifies breathing mechanics.
Conclusion
The pangolin respiratory system is an integrated solution to conflicting demands: olfactory precision requiring large turbinate surface areas, foraging apnoea requiring strong voluntary nasal occlusion musculature, dust exclusion requiring robust mucociliary escalator capacity, and efficient gas exchange during the energetically demanding nocturnal foraging schedule. The anatomical co-evolution of the hyoid-tongue apparatus with laryngeal positioning represents one of the most unusual respiratory-digestive interface designs in the mammal class. In captivity, the collapse of mucociliary defence under chronic stress, combined with novel fungal and bacterial exposures, converts what is a resilient wild respiratory system into a target for the pneumonias that kill a disproportionate number of pangolins in rescue facilities globally. Bridging this gap requires understanding the anatomy well enough to maintain the conditions that keep it functional.